Adding Numbers to 20 Worksheet in Grade 1 - Mathematics - Exercises with solutions

Master adding numbers to 20: counting, adding, and simple arithmetic through these 10 detailed exercises.

Solutions: Exercises 1 to 10
1 Adding 5 + 7
Exercise 1
What is 5 + 7?
Difficulty: Beginner Time: ~1 minute Skills: Basic Addition
Definition:

Addition: The process of combining two or more numbers to find the total amount. The symbol is +.

Note: When adding numbers up to 20, we're working within the range of 0 to 20.

Step-by-step addition method:
  1. Start with the first number (5)
  2. Count up by the second number (7)
  3. Count: 6, 7, 8, 9, 10, 11, 12
  4. Arrive at the answer (12)
First Number
5
Second Number
7
Sum
12
Step 1: Start with the first number

Begin with 5

Step 2: Count up by the second number

Count 7 more: 6, 7, 8, 9, 10, 11, 12

Step 3: Identify the final number

After counting 7 from 5, we reach 12

Step 4: Write the answer

5 + 7 = 12

5 + 7 = 12
Final answer:

5 + 7 = 12.

Applied rules:

• Addition: 5 + 7 = 12

• Counting: Start at 5, count 7 more

• Number sense: Understanding how numbers relate to each other

• Practice Tip: Use your fingers or draw circles to help count

Related Examples:
  • 4 + 6 = 10
  • 3 + 8 = 11
  • 5 + 5 = 10
Quick Tips:
  • Start with the bigger number to count fewer times
  • Use your fingers to help count
  • Draw dots or circles to represent numbers
Frequently Asked Questions:

Q: What if I count wrong?
A: Count again slowly. You can also start with the bigger number to count fewer times.

Q: Can I add in any order?
A: Yes! 5 + 7 = 7 + 5 = 12.

2 Adding 8 + 6
Exercise 2
What is 8 + 6?
Difficulty: Beginner Time: ~1 minute Skills: Basic Addition
Definition:

Counting strategy: When adding two numbers, you can count up from the first number by the amount of the second number.

Note: For 8 + 6, we start at 8 and count 6 more numbers: 9, 10, 11, 12, 13, 14.

Step-by-step addition method:
  1. Start with the first number (8)
  2. Count up by the second number (6)
  3. Count: 9, 10, 11, 12, 13, 14
  4. Arrive at the answer (14)
First Number
8
Second Number
6
Sum
14
Step 1: Start with the first number

Begin with 8

Step 2: Count up by the second number

Count 6 more: 9, 10, 11, 12, 13, 14

Step 3: Identify the final number

After counting 6 from 8, we reach 14

Step 4: Write the answer

8 + 6 = 14

8 + 6 = 14
Final answer:

8 + 6 = 14.

Applied rules:

• Addition: 8 + 6 = 14

• Counting: Start at 8, count 6 more

• Number sense: Understanding how numbers relate to each other

• Practice Tip: Use your fingers or draw circles to help count

Related Examples:
  • 7 + 5 = 12
  • 9 + 4 = 13
  • 6 + 8 = 14
Quick Tips:
  • Start with the bigger number to count fewer times
  • Use your fingers to help count
  • Draw dots or circles to represent numbers
Frequently Asked Questions:

Q: What if I count wrong?
A: Count again slowly. You can also start with the bigger number to count fewer times.

Q: Can I add in any order?
A: Yes! 8 + 6 = 6 + 8 = 14.

3 Adding 9 + 4
Exercise 3
What is 9 + 4?
Difficulty: Beginner Time: ~1 minute Skills: Basic Addition
Definition:

Make ten strategy: When adding numbers close to 10, you can think about how they relate to 10 to make addition easier.

Note: For 9 + 4, think of it as "9 needs 1 more to make 10, so take 1 from 4, leaving 3. That gives us 10 + 3 = 13."

Step-by-step addition method:
  1. Start with the first number (9)
  2. Count up by the second number (4)
  3. Count: 10, 11, 12, 13
  4. Arrive at the answer (13)
First Number
9
Second Number
4
Sum
13
Step 1: Start with the first number

Begin with 9

Step 2: Count up by the second number

Count 4 more: 10, 11, 12, 13

Step 3: Identify the final number

After counting 4 from 9, we reach 13

Step 4: Write the answer

9 + 4 = 13

9 + 4 = 13
Final answer:

9 + 4 = 13.

Applied rules:

• Addition: 9 + 4 = 13

• Counting: Start at 9, count 4 more

• Number sense: Understanding how numbers relate to each other

• Practice Tip: Use your fingers or draw circles to help count

Related Examples:
  • 8 + 3 = 11
  • 7 + 5 = 12
  • 6 + 7 = 13
Quick Tips:
  • Start with the bigger number to count fewer times
  • Use your fingers to help count
  • Draw dots or circles to represent numbers
Frequently Asked Questions:

Q: What if I count wrong?
A: Count again slowly. You can also start with the bigger number to count fewer times.

Q: Can I add in any order?
A: Yes! 9 + 4 = 4 + 9 = 13.

Solutions: Exercises 4 to 5
4 Adding 3 + 12
Exercise 4
What is 3 + 12?
Definition:

Adding to teen numbers: When adding a small number to a teen number, start with the bigger number to count fewer times.

Note: For 3 + 12, it's easier to start with 12 and count 3 more: 13, 14, 15.

Step-by-step addition method:
  1. Start with the bigger number (12)
  2. Count up by the smaller number (3)
  3. Count: 13, 14, 15
  4. Arrive at the answer (15)
First Number
3
Second Number
12
Sum
15
Step 1: Start with the bigger number

Begin with 12 (it's easier to count 3 from 12 than 12 from 3)

Step 2: Count up by the smaller number

Count 3 more: 13, 14, 15

Step 3: Identify the final number

After counting 3 from 12, we reach 15

Step 4: Write the answer

3 + 12 = 15

3 + 12 = 15
Final answer:

3 + 12 = 15.

Applied rules:

• Addition: 3 + 12 = 15

• Counting: Start at 12, count 3 more

• Efficiency: Start with the bigger number to count fewer times

• Practice Tip: Use your fingers or draw circles to help count

Related Examples:
  • 2 + 11 = 13
  • 4 + 13 = 17
  • 5 + 14 = 19
Quick Tips:
  • Always start with the bigger number to count fewer times
  • Use your fingers to help count
  • Draw dots or circles to represent numbers
Frequently Asked Questions:

Q: Should I always start with the bigger number?
A: Yes, it's easier to count fewer numbers from a bigger starting point.

Q: Can I add in any order?
A: Yes! 3 + 12 = 12 + 3 = 15.

5 Adding 11 + 5
Exercise 5
What is 11 + 5?
Definition:

Adding to numbers ending in 1: When adding to 11, think of it as adding to 10 and then adding 1 more.

Note: For 11 + 5, think of it as (10 + 5) + 1 = 15 + 1 = 16.

Step-by-step addition method:
  1. Start with the first number (11)
  2. Count up by the second number (5)
  3. Count: 12, 13, 14, 15, 16
  4. Arrive at the answer (16)
First Number
11
Second Number
5
Sum
16
Step 1: Start with the first number

Begin with 11

Step 2: Count up by the second number

Count 5 more: 12, 13, 14, 15, 16

Step 3: Identify the final number

After counting 5 from 11, we reach 16

Step 4: Write the answer

11 + 5 = 16

11 + 5 = 16
Final answer:

11 + 5 = 16.

Applied rules:

• Addition: 11 + 5 = 16

• Counting: Start at 11, count 5 more

• Number sense: Understanding how numbers relate to each other

• Practice Tip: Use your fingers or draw circles to help count

Related Examples:
  • 11 + 3 = 14
  • 11 + 6 = 17
  • 11 + 8 = 19
Quick Tips:
  • Think of 11 as 10 + 1 to make addition easier
  • Use your fingers to help count
  • Draw dots or circles to represent numbers
Frequently Asked Questions:

Q: Why is 11 special for addition?
A: Because 11 is 10 + 1, so you can add to 10 first, then add 1 more.

Q: Can I add in any order?
A: Yes! 11 + 5 = 5 + 11 = 16.

Solutions: Exercises 6 to 10
6 Adding 7 + 8
Exercise 6
What is 7 + 8?
Definition:

Near doubles strategy: When adding numbers that are close to each other, you can use a doubles fact and adjust slightly.

Note: For 7 + 8, think of 7 + 7 = 14, then add 1 more to get 15, or think of 8 + 8 = 16, then subtract 1 to get 15.

Step-by-step addition method:
  1. Start with the bigger number (8)
  2. Count up by the smaller number (7)
  3. Count: 9, 10, 11, 12, 13, 14, 15
  4. Arrive at the answer (15)
First Number
7
Second Number
8
Sum
15
Step 1: Start with the bigger number

Begin with 8 (easier to count 7 from 8 than 8 from 7)

Step 2: Count up by the smaller number

Count 7 more: 9, 10, 11, 12, 13, 14, 15

Step 3: Identify the final number

After counting 7 from 8, we reach 15

Step 4: Write the answer

7 + 8 = 15

7 + 8 = 15
Final answer:

7 + 8 = 15.

Applied rules:

• Addition: 7 + 8 = 15

• Counting: Start at 8, count 7 more

• Efficiency: Start with the bigger number to count fewer times

• Practice Tip: Near doubles like 7+8 are close to doubles facts

Related Examples:
  • 6 + 7 = 13
  • 8 + 9 = 17
  • 5 + 6 = 11
Quick Tips:
  • Think of near doubles as doubles plus or minus 1
  • Start with the bigger number to count fewer times
  • Use your fingers to help count
Frequently Asked Questions:

Q: What are near doubles?
A: Numbers that are one apart like 6+7, 7+8, 8+9. They're close to doubles facts.

Q: Can I add in any order?
A: Yes! 7 + 8 = 8 + 7 = 15.

7 Adding 6 + 9
Exercise 7
What is 6 + 9?
Definition:

Adding to 9 strategy: When adding to 9, you can think of it as adding to 10 and then subtracting 1.

Note: For 6 + 9, think of it as 6 + 10 = 16, then subtract 1 to get 15.

Step-by-step addition method:
  1. Start with the bigger number (9)
  2. Count up by the smaller number (6)
  3. Count: 10, 11, 12, 13, 14, 15
  4. Arrive at the answer (15)
First Number
6
Second Number
9
Sum
15
Step 1: Start with the bigger number

Begin with 9 (easier to count 6 from 9 than 9 from 6)

Step 2: Count up by the smaller number

Count 6 more: 10, 11, 12, 13, 14, 15

Step 3: Identify the final number

After counting 6 from 9, we reach 15

Step 4: Write the answer

6 + 9 = 15

6 + 9 = 15
Final answer:

6 + 9 = 15.

Applied rules:

• Addition: 6 + 9 = 15

• Counting: Start at 9, count 6 more

• Efficiency: Start with the bigger number to count fewer times

• Practice Tip: Adding to 9 is like adding to 10 then subtracting 1

Related Examples:
  • 4 + 9 = 13
  • 7 + 9 = 16
  • 8 + 9 = 17
Quick Tips:
  • Think of adding 9 as adding 10 then subtracting 1
  • Start with the bigger number to count fewer times
  • Use your fingers to help count
Frequently Asked Questions:

Q: Why is adding to 9 special?
A: Because 9 is one less than 10, you can add to 10 and subtract 1.

Q: Can I add in any order?
A: Yes! 6 + 9 = 9 + 6 = 15.

8 Adding 4 + 15
Exercise 8
What is 4 + 15?
Definition:

Adding to numbers in the teens: When adding a small number to a teen number, start with the bigger number to count fewer times.

Note: For 4 + 15, it's easier to start with 15 and count 4 more: 16, 17, 18, 19.

Step-by-step addition method:
  1. Start with the bigger number (15)
  2. Count up by the smaller number (4)
  3. Count: 16, 17, 18, 19
  4. Arrive at the answer (19)
First Number
4
Second Number
15
Sum
19
Step 1: Start with the bigger number

Begin with 15 (easier to count 4 from 15 than 15 from 4)

Step 2: Count up by the smaller number

Count 4 more: 16, 17, 18, 19

Step 3: Identify the final number

After counting 4 from 15, we reach 19

Step 4: Write the answer

4 + 15 = 19

4 + 15 = 19
Final answer:

4 + 15 = 19.

Applied rules:

• Addition: 4 + 15 = 19

• Counting: Start at 15, count 4 more

• Efficiency: Start with the bigger number to count fewer times

• Practice Tip: When adding to teen numbers, start with the teen number

Related Examples:
  • 3 + 14 = 17
  • 2 + 16 = 18
  • 5 + 13 = 18
Quick Tips:
  • Always start with the bigger number to count fewer times
  • Use your fingers to help count
  • Draw dots or circles to represent numbers
Frequently Asked Questions:

Q: Should I always start with the bigger number?
A: Yes, it's easier to count fewer numbers from a bigger starting point.

Q: Can I add in any order?
A: Yes! 4 + 15 = 15 + 4 = 19.

9 Adding 10 + 8
Exercise 9
What is 10 + 8?
Definition:

Adding to 10 strategy: When adding to 10, the answer is simply the other number with a 1 in front of it.

Note: For 10 + 8, the answer is 18. Adding 10 to any number from 1-9 creates a teen number.

Step-by-step addition method:
  1. Start with the first number (10)
  2. Count up by the second number (8)
  3. Count: 11, 12, 13, 14, 15, 16, 17, 18
  4. Arrive at the answer (18)
First Number
10
Second Number
8
Sum
18
Step 1: Start with the first number

Begin with 10

Step 2: Count up by the second number

Count 8 more: 11, 12, 13, 14, 15, 16, 17, 18

Step 3: Identify the final number

After counting 8 from 10, we reach 18

Step 4: Write the answer

10 + 8 = 18

10 + 8 = 18
Final answer:

10 + 8 = 18.

Applied rules:

• Addition: 10 + 8 = 18

• Counting: Start at 10, count 8 more

• Number sense: Adding 10 creates teen numbers

• Practice Tip: Adding 10 is easy - just put 1 in front of the other number

Related Examples:
  • 10 + 3 = 13
  • 10 + 7 = 17
  • 10 + 9 = 19
Quick Tips:
  • Adding 10 is simple - just put 1 in front of the other number
  • Use your fingers to help count
  • Draw dots or circles to represent numbers
Frequently Asked Questions:

Q: Why is adding 10 so easy?
A: Because 10 is the base of our number system, adding 10 creates teen numbers.

Q: Can I add in any order?
A: Yes! 10 + 8 = 8 + 10 = 18.

10 Adding 13 + 6
Exercise 10
What is 13 + 6?
Definition:

Adding to teen numbers: When adding to a teen number, break it down: add to the ones digit first, then combine with tens.

Note: For 13 + 6, think of it as (10 + 3) + 6 = 10 + (3 + 6) = 10 + 9 = 19.

Step-by-step addition method:
  1. Start with the first number (13)
  2. Count up by the second number (6)
  3. Count: 14, 15, 16, 17, 18, 19
  4. Arrive at the answer (19)
First Number
13
Second Number
6
Sum
19
Step 1: Start with the first number

Begin with 13

Step 2: Count up by the second number

Count 6 more: 14, 15, 16, 17, 18, 19

Step 3: Identify the final number

After counting 6 from 13, we reach 19

Step 4: Write the answer

13 + 6 = 19

13 + 6 = 19
Final answer:

13 + 6 = 19.

Applied rules:

• Addition: 13 + 6 = 19

• Counting: Start at 13, count 6 more

• Number sense: Breaking down teen numbers can make addition easier

• Practice Tip: Add the ones digits first, then combine with tens

Related Examples:
  • 12 + 5 = 17
  • 14 + 4 = 18
  • 15 + 3 = 18
Quick Tips:
  • Break down teen numbers when adding
  • Use your fingers to help count
  • Draw dots or circles to represent numbers
Frequently Asked Questions:

Q: How do I break down teen numbers?
A: Think of them as 10 plus some more: 13 = 10 + 3, 14 = 10 + 4, etc.

Q: Can I add in any order?
A: Yes! 13 + 6 = 6 + 13 = 19.

Key Laws, Methods, Rules, and Definitions
\(a + b = c\)
Addition Formula
Key definitions:

Addition: The process of combining two or more numbers to find the total amount. The symbol is +.

Sum: The answer you get when you add numbers together.

Addends: The numbers being added together.

Complete methodology:
  1. Identify: Find the numbers to add (the addends)
  2. Strategy: Choose the easiest way to add (counting, mental math, etc.)
  3. Calculate: Perform the addition operation
  4. Check: Make sure your answer makes sense
Tip 1: Always start with the bigger number to count fewer times.
Tip 2: Use your fingers or draw pictures to help count.
Tip 3: Adding 10 is easy - just put 1 in front of the other number.
Tip 4: Addition can be done in any order (commutative property).
Common errors: Counting incorrectly, forgetting to carry over, misreading numbers.
Exam preparation: Practice with flashcards, memorize basic facts, check your work.
Formulas to memorize:

• Addition: \(a + b = c\) (where a and b are addends, c is the sum)

• Commutative property: \(a + b = b + a\) (order doesn't matter)

• Identity property: \(a + 0 = a\) (adding zero doesn't change the number)

Rules and Methods for Adding Numbers to 20
\(a + b = c\)
Addition Formula
Addition
\(a + b = c\)
Combine numbers to find total
Commutative
\(a + b = b + a\)
Order doesn't matter
Identity
\(a + 0 = a\)
Adding zero

Key Takeaways

  • Start with the bigger number to count fewer times
  • Use your fingers or draw pictures to help count
  • Addition can be done in any order
  • Adding 10 is easy - just put 1 in front of the other number
  • Check your answer by counting again

Questions & Answers

Question: I have trouble counting. How can I make addition easier?

Answer: Here are some strategies to make addition easier:

  • Use your fingers: Hold up the number of fingers for each number and count them all
  • Draw pictures: Draw circles or dots for each number and count them
  • Count mentally: Start with the bigger number and count up
  • Use objects: Count with blocks, coins, or other small items

Practice regularly to get better at counting and adding!

Question: My child gets confused when adding larger numbers. How can I help?

Answer: Try these approaches to help with larger numbers:

  • Start with the bigger number: Count from the larger number to minimize counting
  • Use ten frames: Visual tools that show how numbers relate to 10
  • Break apart numbers: Add the ones first, then combine with tens
  • Practice with games: Make learning fun with addition games

Consistent practice with concrete examples helps build confidence.

Question: Does it matter which number I add first?

Answer: No, it doesn't matter which number you add first! This is called the commutative property of addition:

  • 5 + 7 = 12 and 7 + 5 = 12
  • 3 + 9 = 12 and 9 + 3 = 12
  • 6 + 8 = 14 and 8 + 6 = 14

However, it's often easier to start with the bigger number so you have fewer numbers to count.

Math Glossary

Addition
The process of combining two or more numbers to find the total amount. The symbol is +.
Sum
The answer you get when you add numbers together.
Addends
The numbers being added together in an addition problem.
Commutative Property
The rule that says you can add numbers in any order and get the same answer.
Identity Property
The rule that says adding zero to any number gives the same number.
Counting Strategy
A method of adding by counting up from one number by the amount of the other number.

Adding Numbers Educational Team

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Our team of experienced elementary school teachers and math specialists creates research-based, student-friendly resources focused on early addition concepts. All content is aligned with Common Core State Standards and reviewed by elementary education experts to ensure accuracy and pedagogical effectiveness.