Number 20 Math Worksheet for Students

Instructions

1. Complete each section in order.
2. Show your thinking with drawings, tallies, number sentences, or words.
3. Use counters, coins, or small objects if you need help.
4. Check your answers when you finish.

Learning Goals

• Count forward and backward within 20.
• Represent 20 in different ways.
• Add and subtract within 20.
• Use math to solve everyday problems.

1. Count to 20

A. Fill in the missing numbers.

1. 1, 2, ___, 4, 5
2. 6, ___, 8, 9, 10
3. 11, 12, ___, 14, 15
4. 16, ___, 18, 19, 20
5. 20, 19, ___, 17, 16
6. 15, ___, 13, 12, 11

B. Circle the numbers that are less than 20.

8  20  14  25  19  30  3

2. Show the Number 20

A. Complete the number bonds.

B. Write two different addition sentences that equal 20.

C. Draw 20 objects.

Use dots, stars, circles, or another shape. Then divide your drawing into two groups and write the matching addition sentence.

Drawing space:

Addition sentence: _____

3. Add Within 20

Solve each problem. You may draw a picture or use a number line.

1. 3 + 4 = __
2. 5 + 6 = __
3. 7 + 2 = __
4. 8 + 5 = __
5. 9 + 7 = __
6. 10 + 8 = __
7. 12 + 4 = __
8. 11 + 9 = __

Hint: For a harder problem, start with the larger number and count forward.

4. Subtract Within 20

Solve each problem.

1. 8 − 3 = __
2. 10 − 6 = __
3. 12 − 5 = __
4. 15 − 7 = __
5. 17 − 8 = __
6. 20 − 10 = __
7. 19 − 4 = __
8. 20 − 13 = __

5. Choose the Correct Sign

Write + or − in each box.

1. 6 □ 3 = 9
2. 10 □ 4 = 6
3. 7 □ 8 = 15
4. 18 □ 5 = 13
5. 9 □ 9 = 18
6. 20 □ 7 = 13

6. Real-World Math Mission

A class is preparing snack bags. Each bag should have 20 items.

1. Maya puts 12 crackers in a bag. How many more crackers are needed?

   Number sentence: __

   Answer: __ more crackers

2. Leo has 8 apple slices and adds 7 more. How many apple slices does he have now?

   Number sentence: __

   Answer: __ apple slices

3. There are 20 grapes. The children eat 9 grapes. How many grapes are left?

   Number sentence: __

   Answer: __ grapes

4. Two snack bags have 10 items each. How many items are there altogether?

   Number sentence: __

   Answer: __ items

7. Match the Problem to the Answer

Write the letter of the correct answer on each line.

1. 4 + 6 = __
2. 16 − 5 = __
3. 9 + 8 = __
4. 20 − 4 = __
5. 7 + 7 = __

• A. 14
• B. 10
• C. 16
• D. 11
• E. 17

8. Explain Your Thinking

Choose one problem from Sections 3 or 4. Explain how you solved it.

Problem: ____

My strategy:

Optional Challenge

1. I am thinking of a number less than 20. It is greater than 14. What numbers could I be thinking of?

   ---

2. Find three different ways to make 20 using addition and subtraction.

   a. _____

   b. _____

   c. _____

3. There are 20 pencils. Some are red and some are blue. What are three possible combinations?

   Red pencils	Blue pencils	Total
   10	10	20
   		20
   		20
   		20

Answer Key

1. Count to 20

A.

1. 3
2. 7
3. 13
4. 17
5. 18
6. 14

B. 8, 14, 19, 3

2. Show the Number 20

A.

• 1 + 19 = 20
• 2 + 18 = 20
• 5 + 15 = 20
• 8 + 12 = 20
• 12 + 8 = 20

B. Answers may vary. Examples: 10 + 10 = 20; 6 + 14 = 20.

C. The drawing should show 20 objects. The addition sentence will vary but must equal 20.

3. Add Within 20

1. 7
2. 11
3. 9
4. 13
5. 16
6. 18
7. 16
8. 20

4. Subtract Within 20

1. 5
2. 4
3. 7
4. 8
5. 9
6. 10
7. 15
8. 7

5. Choose the Correct Sign

1. +
2. −
3. +
4. −
5. +
6. −

6. Real-World Math Mission

1. 20 − 12 = 8 more crackers
2. 8 + 7 = 15 apple slices
3. 20 − 9 = 11 grapes
4. 10 + 10 = 20 items

7. Match the Problem to the Answer

1. B
2. D
3. E
4. C
5. A

8. Explain Your Thinking

Answers will vary. The explanation should include a correct strategy and answer.

Optional Challenge

1. Possible numbers: 15, 16, 17, 18, or 19.
2. Answers may vary. Examples: 10 + 10 = 20; 15 + 5 = 20; 25 − 5 = 20.
3. Answers may vary. Each row must total 20, such as 5 red and 15 blue, 12 red and 8 blue, or 18 red and 2 blue.