Subtraction Practice Within 20 in Grade 1 - Mathematics - Exercises with solutions

Master subtraction within 20: basic subtraction, mental math, and number facts through these 10 detailed exercises.

Solutions: Exercises 1 to 10
1 Basic Subtraction
Exercise 1
What is 12 - 5?
Difficulty: Easy Time: ~2 minutes Skills: Basic Subtraction
Definition:

Subtraction within 20: A basic subtraction operation where both the minuend and subtrahend are numbers from 0 to 20.

Note: These facts form the foundation for more complex subtraction and should be memorized for quick recall.

Step-by-step counting method:
  1. Start with the minuend (12)
  2. Count backward by the subtrahend (5)
  3. Count how many you have left
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12 - 5 = 7
Step 1: Start with 12

We begin at 12 on the number line

Step 2: Count back 5

Move 5 spaces to the left: 12 → 11 → 10 → 9 → 8 → 7

Step 3: Count what remains

We land on 7, so 12 - 5 = 7

12 - 5 = 7
Final answer:

12 - 5 = 7

Applied rules:

• Count back strategy: Move left on number line by subtrahend

• Number relationship: 12 is made up of 5 and 7

• Verification: Add back: 7 + 5 = 12 ✓

• Practice Tip: Count backward: 12, 11, 10, 9, 8, 7 (stop after 5 counts)

Related Examples:
  • 11 - 3 = 8 (start at 11, count back 3)
  • 15 - 6 = 9 (start at 15, count back 6)
  • 18 - 7 = 11 (start at 18, count back 7)
Quick Tips:
  • Use your fingers to count backward
  • Think of subtraction as "taking away"
  • Always verify by adding the answer back to the subtracted number
Frequently Asked Questions:

Q: Can I subtract a bigger number from a smaller number?
A: Not yet! In 1st grade, we only subtract smaller numbers from bigger numbers.

Q: What if I count wrong?
A: Count slowly and carefully. You can also use your fingers to help.

2 Count Back Strategy
Exercise 2
What is 15 - 8?
Difficulty: Easy Time: ~2 minutes Skills: Count Back Strategy
Definition:

Count back strategy: Starting from the minuend and counting backward by the number of steps equal to the subtrahend.

Note: This strategy helps build number sense and is a bridge to mental subtraction without physical counting.

Step-by-step count back method:
  1. Start with the minuend (first number)
  2. Count backward one number at a time
  3. Stop after counting back the number of steps equal to the subtrahend
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15 - 8 = 7
Step 1: Start at 15

We begin counting from 15

Step 2: Count back 8 steps

15 → 14 → 13 → 12 → 11 → 10 → 9 → 8 → 7 (that's 8 steps)

Step 3: Record the final number

We land on 7, so 15 - 8 = 7

15 - 8 = 7
Final answer:

15 - 8 = 7

Applied rules:

• Sequential counting: Count each number as you move back

• Step tracking: Keep track of how many steps you've taken

• Stopping rule: Stop after the number of steps equals the subtrahend

• Practice Tip: Use fingers to track the steps: 15, 14, 13, 12, 11, 10, 9, 8, 7

Related Examples:
  • 14 - 6 = 8 (14, 13, 12, 11, 10, 9, 8)
  • 17 - 9 = 8 (17, 16, 15, 14, 13, 12, 11, 10, 9, 8)
  • 13 - 5 = 8 (13, 12, 11, 10, 9, 8)
Quick Tips:
  • Use your fingers to keep track of steps
  • Count out loud to stay focused
  • Start with the larger number and count backward
Frequently Asked Questions:

Q: What if I lose track while counting back?
A: Use your fingers to track each step, or start over and count more slowly.

Q: Can I count forward instead?
A: Counting back is the subtraction strategy. Counting forward is for addition.

3 Number Bonds
Exercise 3
What is 13 - 4?
Difficulty: Easy Time: ~2 minutes Skills: Number Bonds
Definition:

Number bond: A visual representation showing how numbers can be split into parts that make up the whole number.

Note: Number bonds help understand the relationship between addition and subtraction, showing that 13 can be broken into 4 and 9.

Step-by-step number bond method:
  1. Identify the whole number (minuend)
  2. Identify one part (subtrahend)
  3. Find the missing part (difference)
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13 - 4 = 9
Step 1: Understand the whole

13 is the whole number we start with

Step 2: Identify one part

4 is the part we are taking away

Step 3: Find the missing part

What part combines with 4 to make 13? Answer: 9

13 - 4 = 9
Final answer:

13 - 4 = 9

Applied rules:

• Part-whole relationship: 13 = 4 + 9, so 13 - 4 = 9

• Addition connection: Subtraction reverses addition

• Number bond: Shows how numbers relate to each other

• Practice Tip: Remember: if 4 + 9 = 13, then 13 - 4 = 9

Related Examples:
  • 11 - 3 = 8 because 3 + 8 = 11
  • 16 - 7 = 9 because 7 + 9 = 16
  • 14 - 6 = 8 because 6 + 8 = 14
Quick Tips:
  • Think of subtraction as finding a missing part
  • Use addition facts to help with subtraction
  • If you know 5 + 8 = 13, then 13 - 5 = 8
Frequently Asked Questions:

Q: How are addition and subtraction connected?
A: They are opposite operations. If 5 + 8 = 13, then 13 - 5 = 8 and 13 - 8 = 5.

Q: What are number bonds good for?
A: They help you see how numbers fit together and make mental math easier.

Solutions: Exercises 4 to 5
4 Missing Numbers
Exercise 4
16 - ? = 7. What number goes in the blank?
Definition:

Missing number subtraction: Finding the unknown subtrahend in a subtraction equation where the minuend and difference are known.

Note: This helps develop algebraic thinking early by understanding the relationship between the parts of a subtraction equation.

Step-by-step missing number method:
  1. Start with the minuend (16)
  2. Think about what needs to be subtracted to get the difference (7)
  3. Count how many steps from difference back to minuend
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16 - 9 = 7
Step 1: Analyze the equation

We have 16 - ? = 7, so we need to find what number subtracted from 16 gives us 7

Step 2: Think about the relationship

16 is made up of 7 and another number. If 16 = 7 + ?, then ? = 16 - 7 = 9

Step 3: Verify the answer

Check: 16 - 9 = 7 ✓

16 - 9 = 7
Final answer:

The missing number is 9.

Applied rules:

• Relationship understanding: Minuend - Subtrahend = Difference

• Reversibility: Difference + Subtrahend = Minuend

• Verification: Always check your answer by substituting back

• Practice Tip: Think: "What number added to 7 makes 16?" Answer: 9

Related Examples:
  • 15 - ? = 8, so ? = 7 because 15 - 7 = 8
  • 18 - ? = 9, so ? = 9 because 18 - 9 = 9
  • 14 - ? = 6, so ? = 8 because 14 - 8 = 6
Quick Tips:
  • Think of subtraction as "what to take away"
  • Use addition to check: if 16 - ? = 7, then 7 + ? = 16
  • Count from the answer to the starting number
Frequently Asked Questions:

Q: How do I know which number is missing?
A: Look at the equation format: Minuend - Subtrahend = Difference. Usually the subtrahend is missing.

Q: Can the missing number be bigger than the starting number?
A: No, in subtraction the number being subtracted must be equal to or less than the starting number.

5 Fact Families
Exercise 5
If 8 + 5 = 13, what are the related subtraction facts?
Definition:

Fact family: A group of related addition and subtraction facts that use the same three numbers.

Note: Fact families show the inverse relationship between addition and subtraction, helping students understand how operations connect.

Step-by-step fact family method:
  1. Identify the three numbers in the family (8, 5, 13)
  2. Create two addition facts
  3. Create two subtraction facts
8 + 5 = 13
5 + 8 = 13
13 - 5 = 8
13 - 8 = 5
Step 1: Identify the three numbers

From 8 + 5 = 13, our numbers are 8, 5, and 13

Step 2: Create addition facts

8 + 5 = 13 and 5 + 8 = 13 (commutative property)

Step 3: Create subtraction facts

13 - 5 = 8 and 13 - 8 = 5 (starting with the largest number)

13 - 5 = 8 and 13 - 8 = 5
Final answer:

The related subtraction facts are: 13 - 5 = 8 and 13 - 8 = 5

Applied rules:

• Fact family principle: Three numbers create four related facts

• Inverse operations: Addition and subtraction reverse each other

• Commutative property: Order doesn't matter in addition

• Practice Tip: Always start subtraction facts with the largest number

Related Examples:
  • If 7 + 4 = 11: 4 + 7 = 11, 11 - 4 = 7, 11 - 7 = 4
  • If 9 + 2 = 12: 2 + 9 = 12, 12 - 2 = 9, 12 - 9 = 2
  • If 6 + 8 = 14: 8 + 6 = 14, 14 - 8 = 6, 14 - 6 = 8
Quick Tips:
  • Always start subtraction facts with the biggest number
  • Know one fact, and you know three others
  • Fact families help with both addition and subtraction
Frequently Asked Questions:

Q: Why do we learn fact families?
A: They show how addition and subtraction are connected and help with mental math.

Q: Do all numbers make fact families?
A: Any three numbers that work in addition/subtraction can form a family.

Solutions: Exercises 6 to 10
6 Zero Facts
Exercise 6
What is 14 - 0?
Definition:

Zero subtraction fact: Any number minus zero equals the original number (identity property of subtraction).

Note: This demonstrates that subtracting zero doesn't change the value of a number, which is fundamental to understanding subtraction properties.

Step-by-step zero method:
  1. Start with the original number
  2. Understand that subtracting zero means taking nothing away
  3. Therefore, the number remains unchanged
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14 - 0 = 14
Step 1: Understand the operation

We're subtracting zero, which means we're not taking anything away

Step 2: Apply the zero property

Any number minus zero equals itself: 14 - 0 = 14

Step 3: Verify the result

Adding back: 14 + 0 = 14, confirming our answer

14 - 0 = 14
Final answer:

14 - 0 = 14

Applied rules:

• Identity property: Any number minus zero equals itself

• Zero concept: Zero represents nothing, so nothing changes

• Verification: Adding zero doesn't change the number

• Practice Tip: Remember: subtracting zero keeps the number the same

Related Examples:
  • 12 - 0 = 12 (subtracting nothing keeps it the same)
  • 17 - 0 = 17 (no change when subtracting zero)
  • 9 - 0 = 9 (zero doesn't affect the number)
Quick Tips:
  • Zero means nothing is taken away
  • The number always stays the same when subtracting zero
  • This works for any number
Frequently Asked Questions:

Q: Why does subtracting zero not change the number?
A: Because zero represents nothing, so taking away nothing leaves everything unchanged.

Q: Does this work for big numbers too?
A: Yes! Any number minus zero equals itself, no matter how big.

7 Same Number Facts
Exercise 7
What is 15 - 15?
Definition:

Same number subtraction: Any number minus itself equals zero (subtraction property of equality).

Note: This demonstrates that taking away the entire amount leaves nothing remaining, which is fundamental to understanding subtraction.

Step-by-step same number method:
  1. Start with the number
  2. Subtract the same number (take away everything)
  3. Result is always zero
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15 - 15 = 0
Step 1: Understand the operation

We're taking away all 15 objects from the 15 we started with

Step 2: Apply the same number property

Any number minus itself equals zero: 15 - 15 = 0

Step 3: Verify the result

Adding back: 0 + 15 = 15, confirming our answer

15 - 15 = 0
Final answer:

15 - 15 = 0

Applied rules:

• Subtraction property: Any number minus itself equals zero

• Takeaway concept: Taking away everything leaves nothing

• Verification: Adding the number back gives the original

• Practice Tip: Remember: taking away all of something leaves zero

Related Examples:
  • 11 - 11 = 0 (taking away all 11 leaves 0)
  • 18 - 18 = 0 (taking away all 18 leaves 0)
  • 7 - 7 = 0 (taking away all 7 leaves 0)
Quick Tips:
  • When you subtract a number from itself, always get zero
  • Think: "If I have 15 cookies and eat all 15, how many are left?"
  • This works for any number
Frequently Asked Questions:

Q: Why does any number minus itself equal zero?
A: Because you're taking away everything you started with, leaving nothing.

Q: Does this work with bigger numbers?
A: Yes! 100 - 100 = 0, 1000 - 1000 = 0, etc.

8 Mental Math
Exercise 8
What is 19 - 12?
Definition:

Mental math: Performing calculations in your head without physical counting or writing.

Note: Mental math builds number fluency and is essential for developing mathematical confidence and speed.

Step-by-step mental math method:
  1. Think about what number added to 12 makes 19
  2. Recall the number bond: 12 + 7 = 19
  3. Therefore, 19 - 12 = 7
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19 - 12 = 7
Step 1: Use number bond thinking

Think: "12 + ? = 19", so the answer is 7

Step 2: Apply the relationship

Since 12 + 7 = 19, then 19 - 12 = 7

Step 3: Verify mentally

Check: 7 + 12 = 19 ✓

19 - 12 = 7
Final answer:

19 - 12 = 7

Applied rules:

• Number bond recall: Know that 12 + 7 = 19

• Addition-subtraction connection: Use addition facts for subtraction

• Mental verification: Check answer mentally

• Practice Tip: Memorize pairs that make common totals: 10, 15, 20

Related Examples:
  • 17 - 8 = 9 (because 8 + 9 = 17)
  • 16 - 9 = 7 (because 9 + 7 = 16)
  • 18 - 11 = 7 (because 11 + 7 = 18)
Quick Tips:
  • Memorize number bonds for quick recall
  • Use addition facts to help with subtraction
  • Practice mental math regularly
Frequently Asked Questions:

Q: How can I get better at mental math?
A: Practice number bonds, use addition to help with subtraction, and do daily drills.

Q: Should I always use mental math?
A: Start with mental math for facts within 20, but it's okay to count when learning.

9 Word Problems
Exercise 9
Sarah has 16 stickers. She gives 9 stickers to her friend. How many stickers does Sarah have now?
Definition:

Subtraction word problem: A real-life scenario that requires subtraction to find the answer.

Note: Word problems connect mathematical concepts to practical situations, helping students understand the relevance of math.

Step-by-step word problem method:
  1. Read the problem carefully
  2. Identify the starting amount (minuend)
  3. Identify what is taken away (subtrahend)
  4. Set up the subtraction equation
  5. Solve and answer in context
Step 1: Identify the starting amount

Sarah starts with 16 stickers

Step 2: Identify what is taken away

She gives away 9 stickers

Step 3: Set up the equation

16 - 9 = ?

Step 4: Solve the equation

16 - 9 = 7

Step 5: Answer in context

Sarah has 7 stickers now

16 - 9 = 7
Final answer:

Sarah has 7 stickers now.

Applied rules:

• Problem analysis: Identify key information in word problems

• Context understanding: Connect math to real situations

• Application: Use subtraction facts in practical scenarios

• Practice Tip: Look for words like "gives," "takes," "eats," "loses" for subtraction

Related Examples:
  • Tom has 14 marbles, loses 6 → 14 - 6 = 8 marbles left
  • Maria has 18 candies, eats 9 → 18 - 9 = 9 candies left
  • David has 13 books, gives 5 → 13 - 5 = 8 books left
Quick Tips:
  • Look for keywords that indicate subtraction
  • Draw pictures to visualize the problem
  • Always answer in the context of the problem
Frequently Asked Questions:

Q: What words tell me to subtract?
A: Words like "gives," "takes," "eats," "loses," "spends," "removes," "left," "remain."

Q: How do I know what numbers to use?
A: Look for the starting amount and the amount being taken away.

10 Mixed Practice
Exercise 10
Solve these subtraction facts: 18 - 9, 13 - 6, 17 - 17, 15 - 0
Definition:

Mixed subtraction facts: A variety of subtraction problems within 20 to practice fluency and recall.

Note: Mixed practice helps consolidate learning and builds automaticity with basic subtraction facts.

Step-by-step mixed facts method:
  1. Recognize each individual fact
  2. Apply the appropriate strategy for each
  3. Solve each equation separately
  4. Verify answers when possible
18 - 9 = 9
13 - 6 = 7
17 - 17 = 0
15 - 0 = 15
Step 1: Solve 18 - 9

Think: 9 + 9 = 18, so 18 - 9 = 9

Step 2: Solve 13 - 6

Count back: 13 → 12 → 11 → 10 → 9 → 8 → 7, so 13 - 6 = 7

Step 3: Solve 17 - 17

Same number property: 17 - 17 = 0

Step 4: Solve 15 - 0

Zero property: 15 - 0 = 15

18 - 9 = 9, 13 - 6 = 7, 17 - 17 = 0, 15 - 0 = 15
Final answer:

18 - 9 = 9, 13 - 6 = 7, 17 - 17 = 0, 15 - 0 = 15

Applied rules:

• Mixed strategy application: Use different methods for different facts

• Property recognition: Identify zero and same number properties

• Fluency building: Practice various combinations for automaticity

• Practice Tip: Regular mixed practice strengthens all subtraction skills

Related Examples:
  • 16 - 7 = 9 (count back or number bond)
  • 14 - 14 = 0 (same number property)
  • 12 - 0 = 12 (zero property)
  • 20 - 13 = 7 (think 13 + 7 = 20)
Quick Tips:
  • Practice different types of facts regularly
  • Recognize special cases like zero and same number facts
  • Use the most efficient strategy for each fact
Frequently Asked Questions:

Q: How can I get faster at solving mixed facts?
A: Practice regularly, memorize facts, and recognize patterns quickly.

Q: Should I memorize all facts within 20?
A: Yes, knowing these facts automatically helps with harder math later.

Key Laws, Methods, Rules, and Definitions
Minuend - Subtrahend = Difference
Basic Subtraction Formula
Key definitions:

Subtraction: The operation of taking away objects from a group to find what remains.

Minuend: The number from which another number is subtracted (the starting amount).

Subtrahend: The number being subtracted (the amount taken away).

Difference: The result of subtraction (what remains).

Fact Family: A group of related addition and subtraction facts using the same three numbers.

Number Bond: A visual representation showing how numbers can be split into parts.

Complete methodology:
  1. Identify the problem: Recognize the minuend and subtrahend
  2. Choose a strategy: Count back, use number bonds, or recall facts
  3. Perform subtraction: Execute the chosen method
  4. Verify: Check by adding the difference and subtrahend
Tip 1: Memorize pairs that make common totals: 10, 15, 20.
Tip 2: Any number minus itself equals zero.
Tip 3: Any number minus zero equals itself.
Tip 4: Use addition facts to help with subtraction.
Common errors: Counting wrong, forgetting that subtracting zero doesn't change the number, subtracting a larger number from a smaller one.
Practice strategies: Use number lines, practice with manipulatives, drill facts regularly, play math games.
Important rules to remember:

• Subtraction basics: You can only subtract up to the amount you started with

• Zero property: n - 0 = n (any number minus zero equals itself)

• Same number property: n - n = 0 (any number minus itself equals zero)

• Addition connection: If a + b = c, then c - a = b and c - b = a

• Verification: Always check by adding the difference to the subtrahend

Rules and Methods for Subtraction Within 20
a - b = c means a = b + c
Subtraction-Addition Relationship

Subtraction Within 20 Concepts

➖
Subtraction
Taking away objects from a group
🔢
Within 20
Numbers from 0 to 20 only
🧠
Mental Math
Calculating in your head
📚
Fact Families
Related addition and subtraction facts
Key Subtraction Strategies
1
Count back: Start at minuend and count backward
2
Use number bonds: Think of addition facts to solve subtraction
3
Recognize special cases: Same number and zero facts
4
Memorize facts: Know them automatically
Zero Property
n - 0 = n
Subtracting zero changes nothing
Same Number Property
n - n = 0
Taking away all leaves zero

Key Takeaways

  • Subtraction means taking away objects from a group
  • Subtraction facts within 20 should be memorized for fluency
  • Use addition facts to help solve subtraction problems
  • Special properties: n - 0 = n and n - n = 0
  • Fact families connect addition and subtraction

Questions & Answers

Question: My child struggles with subtraction facts within 20. How can I help them memorize these facts effectively?

Answer: Here are effective strategies for memorizing subtraction facts:

  • Build on addition: Use known addition facts to derive subtraction facts (if 8 + 5 = 13, then 13 - 8 = 5)
  • Focus on patterns: Teach special cases like subtracting zero and same number facts
  • Use visual aids: Number lines, counters, and drawings to reinforce concepts
  • Practice regularly: Short, frequent sessions are more effective than long ones
  • Make it fun: Use games, apps, and hands-on activities

Consistency and patience are key. Start with easier facts and gradually build complexity.

Question: Why do we learn fact families? They seem confusing with so many numbers.

Answer: Fact families help you see the connection between addition and subtraction:

  • One fact becomes four: Know 8 + 5 = 13, and you know 5 + 8 = 13, 13 - 5 = 8, and 13 - 8 = 5
  • Understanding relationships: Addition and subtraction are opposite operations
  • Mental math: Helps you solve problems more quickly
  • Checking work: Use addition to verify subtraction answers

Once you understand the pattern, fact families make math easier, not harder!

Question: How can I tell if my child has mastered subtraction facts within 20?

Answer: Signs of mastery include:

  • Automatic recall: Answers come quickly without counting
  • Accuracy: Consistently correct answers across different problem types
  • Application: Successfully solving word problems using subtraction
  • Flexibility: Using different strategies appropriately
  • Confidence: Approaching problems without anxiety

Mastery typically means solving facts within 2-3 seconds per problem with 95% accuracy.

Detailed Summary

This comprehensive guide covers subtraction practice within 20, a fundamental skill in 1st grade mathematics that builds number sense and prepares students for more complex arithmetic. Students learn to subtract numbers from 0 to 20, developing both conceptual understanding and procedural fluency through various strategies and representations.

Core Concepts and Definitions
  • Subtraction: The mathematical operation of taking away objects from a group to find what remains. Represented by the minus sign (-).
  • Minuend: The number from which another number is subtracted; the starting amount in a subtraction problem.
  • Subtrahend: The number being subtracted; the amount taken away from the minuend.
  • Difference: The result of a subtraction problem; what remains after subtracting.
  • Subtraction Facts Within 20: Basic subtraction equations where all numbers are 20 or less, meant for memorization and quick recall.
  • Fact Family: A group of related addition and subtraction facts using the same three numbers.
Core Rules and Principles
  • Subtraction Basics: You can only subtract up to the amount you started with. Cannot subtract a larger number from a smaller number (at this level).
  • Zero Property: Any number minus zero equals the original number (n - 0 = n).
  • Same Number Property: Any number minus itself equals zero (n - n = 0).
  • Addition Connection: If a + b = c, then c - a = b and c - b = a.
  • Verification Rule: Difference + Subtrahend = Minuend. Always check by adding back.
Step-by-Step Methods and Procedures
  • Count Back Method: Start at minuend and count backward by subtrahend steps.
  • Number Bond Method: Think of the relationship between numbers: if 13 = 5 + 8, then 13 - 5 = 8.
  • Addition Strategy: Use known addition facts to solve subtraction: if 8 + 7 = 15, then 15 - 8 = 7.
  • Fact Family Approach: Learn four related facts together using the same three numbers.
  • Verification Method: After solving, add the answer to the subtracted number to check.
Examples (Simple to Advanced)
  • Simple: 12 - 5 = 7 (basic subtraction)
  • Zero Fact: 14 - 0 = 14 (zero property)
  • Same Number: 16 - 16 = 0 (same number property)
  • Using Addition: 19 - 11 = 8 (because 11 + 8 = 19)
  • Fact Family: 7 + 6 = 13, 6 + 7 = 13, 13 - 6 = 7, 13 - 7 = 6
Tips, Tricks, and Common Pitfalls
  • Tips: Memorize pairs that make common totals, use addition to help with subtraction, practice regularly.
  • Tricks: Count backward on number line, use fingers, recognize special cases.
  • Common Pitfalls: Trying to subtract larger from smaller, forgetting zero properties, counting incorrectly.
  • Error Prevention: Always verify by adding back, double-check starting number.
  • Memory Aids: "Zero changes nothing," "same number gives zero," "addition reverses subtraction."
Key Notes for Memorization
  • All subtraction facts within 20 should be memorized for fluency
  • Subtraction is the opposite of addition
  • n - 0 = n (subtracting zero keeps the number)
  • n - n = 0 (subtracting itself gives zero)
  • Know pairs that make common totals: 10, 15, 20
Explanation for Students

Subtraction facts within 20 help you take away small numbers quickly in your head. When you see a subtraction problem, think about what number you need to take away from the first number to get the answer. Remember special rules: taking away zero doesn't change the number, and taking away the same number always gives zero. Use addition facts you know to help with subtraction. Practice these facts until you can answer them quickly without counting.

Math Glossary

Subtraction
The mathematical operation of taking away objects from a group to find what remains. Represented by the minus sign (-).
Minuend
The number from which another number is subtracted; the starting amount in a subtraction problem.
Subtrahend
The number being subtracted; the amount taken away from the minuend.
Difference
The result of a subtraction problem; what remains after subtracting.
Fact Family
A group of related addition and subtraction facts using the same three numbers.
Subtraction Facts Within 20
Basic subtraction equations where all numbers are 20 or less, meant for memorization and quick recall.

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