20 Questions Rules - Subtraction Concepts in Grade 1 - Mathematics - Exercises with solutions

Master subtraction concepts through 20 detailed exercises with visual solutions and interactive learning tools.

Solutions: Exercises 1 to 5
1 Basic Subtraction
Exercise 1
How do I solve 5 - 3 using visual counting?
Difficulty: Beginner Time: ~2 minutes Skills: Counting Backwards
Definition:

Subtraction: Taking away a smaller number from a larger number to find the difference

Note: Subtraction is the opposite of addition. We count backwards to find how many are left.

Step-by-step subtraction method:
  1. Start with the first number (5)
  2. Count backwards the number you are subtracting (3)
  3. Count: 4, 3, 2 (we counted 3 numbers backwards)
  4. The answer is the last number you land on (2)
Original Problem
5 - 3
Visual Representation
⭐⭐⭐⭐⭐ - ⭐⭐⭐ = ⭐⭐
Answer
2
Step 1: Start with 5 objects

We have 5 stars: ⭐⭐⭐⭐⭐

Step 2: Take away 3 objects

We remove 3 stars: ⭐⭐⭐

Step 3: Count remaining objects

We have 2 stars left: ⭐⭐

5 - 3 = 2
Final answer:

5 - 3 = 2

Applied rules:

• Counting backwards: Start with the first number and count backward

• Visual representation: Draw objects to represent the numbers

• Verification: Add the answer to the subtracted number to check: 2 + 3 = 5 ✓

• Practice Tip: Use fingers or counters to physically remove objects

Related Examples:
  • 4 - 2 = 2 - Practice with smaller numbers
  • 6 - 1 = 5 - Practice with single subtraction
  • 3 - 3 = 0 - Practice with equal numbers
Quick Tips:
  • Always start with the bigger number when subtracting
  • Use physical objects like blocks or fingers to visualize
  • Check your answer by adding the result back to the subtracted number
Frequently Asked Questions:

Q: What happens if I subtract a bigger number from a smaller number?
A: In grade 1, we focus on subtracting smaller numbers from bigger numbers to get positive answers.

Q: Can I subtract zero from a number?
A: Yes! Any number minus zero equals itself. Example: 5 - 0 = 5.

2 Visual Subtraction
Exercise 2
Tom has 7 apples. He eats 4 apples. How many apples does he have left?
Difficulty: Beginner Time: ~3 minutes Skills: Word Problems
Definition:

Word problem: A math question written in sentence form that requires subtraction

Note: Look for keywords like "left," "remaining," "take away," or "how many more" to identify subtraction.

Step-by-step word problem method:
  1. Read the problem carefully
  2. Identify the starting amount (7 apples)
  3. Identify what is taken away (4 apples)
  4. Set up the subtraction equation (7 - 4)
  5. Solve the subtraction
Problem
7 apples - 4 apples
Visual
🍎🍎🍎🍎🍎🍎🍎 - 🍎🍎🍎🍎 = 🍎🍎🍎
Answer
3 apples
Step 1: Identify starting amount

Tom starts with 7 apples: 🍎🍎🍎🍎🍎🍎🍎

Step 2: Identify what is taken

He eats 4 apples: 🍎🍎🍎🍎

Step 3: Solve the subtraction

7 - 4 = 3 apples remaining

7 - 4 = 3
Final answer:

Tom has 3 apples left.

Applied rules:

• Word identification: Look for subtraction keywords in the problem

• Visual representation: Draw pictures to represent the problem

• Verification: Check if 3 + 4 = 7 to confirm answer ✓

• Practice Tip: Always answer with the full sentence including units

Related Examples:
  • Sara has 6 candies, gives away 2 → 6 - 2 = 4 candies left
  • Birds on tree: 8 - 3 = 5 birds remaining
  • Toy cars: 5 - 1 = 4 cars left
Quick Tips:
  • Draw circles or dots to represent objects mentioned in the problem
  • Cross out the objects being taken away
  • Always include the unit (apples, cars, etc.) in your final answer
Frequently Asked Questions:

Q: How do I know if a word problem needs subtraction?
A: Look for words like "left," "remaining," "take away," "less," "fewer," or "spend."

Q: Should I always draw pictures?
A: Drawing helps visualize the problem, especially when starting out. As you get better, you might not need to draw every time.

Solutions: Exercises 3 to 5
3 Number Line Subtraction
Exercise 3
How do I solve 8 - 5 using a number line?
Definition:

Number line: A straight line with numbers placed at equal intervals, used to visualize addition and subtraction

Note: Moving left on the number line represents subtraction, moving right represents addition.

Step-by-step number line method:
  1. Start at the first number (8) on the number line
  2. Move left the number of spaces you are subtracting (5)
  3. Count each move: 7, 6, 5, 4, 3
  4. The number you land on is the answer (3)
Problem
8 - 5
Number Line
← ← ← ← ←
Answer
3
Step 1: Start at 8

Place your finger on the number 8 on the number line

Step 2: Move left 5 spaces

Move left: 7 → 6 → 5 → 4 → 3

Step 3: Read the final position

You land on 3, which is the answer

8 - 5 = 3
Final answer:

8 - 5 = 3

Applied rules:

• Direction matters: Left movement represents subtraction

• Count each move: Each space moved represents one number

• Verification: Check if 3 + 5 = 8 to confirm answer ✓

• Practice Tip: Use your finger to physically trace the movement on the number line

Related Examples:
  • 6 - 2 = 4 - Start at 6, move left 2 spaces
  • 9 - 3 = 6 - Start at 9, move left 3 spaces
  • 7 - 7 = 0 - Start at 7, move left 7 spaces
Quick Tips:
  • Always start at the first number in the subtraction
  • Move left for subtraction, right for addition
  • Count each hop to ensure accuracy
Frequently Asked Questions:

Q: What if I go past zero on the number line?
A: In grade 1, we focus on problems that don't go below zero. We always subtract a smaller number from a larger number.

Q: Can I use the number line for addition too?
A: Yes! For addition, move right on the number line instead of left.

4 Word Problem Subtraction
Exercise 4
There are 10 children on a bus. 6 children get off at the stop. How many children are left on the bus?
Definition:

Multi-step word problem: A problem that requires identifying key information and applying subtraction to solve a real-world scenario

Note: Break down the problem into smaller parts: identify total, identify taken away, then subtract.

Step-by-step word problem method:
  1. Read the entire problem carefully
  2. Identify the total amount (10 children)
  3. Identify what is being taken away (6 children getting off)
  4. Write the subtraction equation (10 - 6)
  5. Solve and state the complete answer
Total
10 children
Taken Away
6 children
Remaining
4 children
Step 1: Identify the total

There were 10 children on the bus initially

Step 2: Identify what is removed

6 children got off the bus

Step 3: Set up and solve

10 - 6 = 4 children remaining on the bus

10 - 6 = 4
Final answer:

There are 4 children left on the bus.

Applied rules:

• Information extraction: Identify key numbers and actions in the problem

• Equation setup: Convert words into a mathematical equation

• Verification: Check if 4 + 6 = 10 to confirm answer ✓

• Complete answer: Include the context in your final answer

Related Examples:
  • Books on shelf: 8 - 3 = 5 books remaining
  • Cookies in jar: 9 - 4 = 5 cookies left
  • Students in class: 12 - 5 = 7 students present
Quick Tips:
  • Circle or underline important numbers in the problem
  • Ask yourself: "What am I starting with?" and "What am I taking away?"
  • Always answer with a complete sentence that includes the question's context
Frequently Asked Questions:

Q: What if the problem has extra information?
A: Focus only on the numbers and actions related to the question being asked. Ignore unnecessary details.

Q: How do I know which number to start with?
A: Start with the total amount before anything is taken away. This is usually the larger number.

Rules and Methods for Subtraction Concepts
a - b = c
Basic Subtraction Formula
Rule 1
Start with larger number
Minuend > Subtrahend
Rule 2
Count backwards
Take away method
Rule 3
Check with addition
c + b = a

Key Takeaways

  • Subtraction means taking away or finding the difference
  • Always start with the larger number in grade 1 problems
  • Use visual aids like drawings or number lines to understand
  • Check your answer by adding the result back to the subtracted number
  • Word problems require identifying key information before calculating

Subtraction Strategies

🔢
Count Back Strategy
Start with the first number and count backward. For 7-3: 7, 6, 5, 4
Number Line Method
Start at first number, move left by the second number
Visual Representation
Draw objects and cross out the ones being subtracted
Key Laws, Methods, Rules, and Definitions
Minuend - Subtrahend = Difference
Subtraction Components
Key definitions:

Minuend: The first number in subtraction (what you start with)

Subtrahend: The second number in subtraction (what you take away)

Difference: The result of subtraction (what's left over)

Complete methodology:
  1. Identify components: Recognize minuend, subtrahend, and what you're looking for
  2. Choose strategy: Counting back, number line, or visual representation
  3. Execute calculation: Follow the chosen method systematically
  4. Verify result: Add the difference to the subtrahend to check
Tip 1: Use your fingers to count backward when subtracting small numbers.
Tip 2: Draw circles to represent numbers, then cross out the ones being subtracted.
Tip 3: Always check your answer by adding the result back to the number you subtracted.
Tip 4: In grade 1, subtraction always results in a positive number or zero.
Common errors: Subtracting larger from smaller numbers, miscounting, forgetting to check answers, confusing addition and subtraction.
Success strategies: Use visual aids, practice with manipulatives, check answers, read word problems carefully.
Key concepts to master:

• Subtraction as taking away: removing objects from a group

• Subtraction as comparison: finding the difference between two amounts

• Subtraction facts: knowing combinations like 5-2=3 automatically

• Relationship to addition: subtraction is the inverse operation of addition

• Word problem keywords: recognizing "left," "remaining," "take away," "less than"

Questions & Answers

Question: Why do we subtract numbers? When do we use subtraction in real life?

Answer: Great question! We subtract numbers to find out how many are left or to compare amounts. Here are real-life examples:

  • When you eat 3 cookies from a plate of 8: 8 - 3 = 5 cookies left
  • When you spend $2 from $5: 5 - 2 = 3 dollars remaining
  • When 4 friends leave a group of 7: 7 - 4 = 3 friends stay
  • Comparing ages: If you're 7 and your sister is 5, you're 7 - 5 = 2 years older

Subtraction helps us understand changes in quantities and make comparisons between different amounts.

Question: My child struggles with word problems. How can I help them identify when to subtract?

Answer: Help your child look for subtraction clue words in problems:

  • Taking away: "gave away," "ate," "lost," "sold," "used"
  • Remaining: "left," "remaining," "still have," "not used"
  • Comparison: "more than," "less than," "fewer," "difference"

Practice with simple scenarios: "You had 6 stickers and gave 2 to your friend. How many do you have left?" Encourage drawing pictures to visualize the situation.

Also, teach the "think addition" strategy: If 7 - ? = 4, think "4 + ? = 7" to find the missing number.

Question: I sometimes get confused between addition and subtraction. How can I remember the difference?

Answer: Think of addition and subtraction like this:

  • Addition (+): Getting MORE - putting things together, combining groups
  • Subtraction (-): Getting FEWER - taking away, finding what's left

Memory trick: "Add" sounds like "all together" (combining), and "subtract" sounds like "stray" (taking away).

Practice with your hands: Addition = bringing hands together, Subtraction = pulling hands apart. The + sign looks like two lines coming together, the - sign is just one line going away.

Math Glossary

Subtraction
The operation of taking away one number from another to find the difference. Symbol: minus (-).
Minuend
The first number in a subtraction problem; the number you start with before taking away.
Subtrahend
The second number in a subtraction problem; the number being taken away from the minuend.
Difference
The result or answer in a subtraction problem; what's left after subtracting.
Number Line
A visual tool with numbers placed at equal intervals along a straight line, used to perform addition and subtraction.

Math Excellence Educational Team

Certified Elementary Mathematics Educators & Curriculum Specialists

Our team of experienced elementary math teachers and curriculum developers creates research-based, student-friendly subtraction resources. All content is aligned with Common Core State Standards and reviewed by mathematics education experts to ensure accuracy and pedagogical effectiveness for young learners.