Addition Within 20 — Answer Key
Part A: Multiple Choice
Circle the correct answer for each question.
1. On a number line, you start at 6 and jump 9 spaces forward. Where do you land?
A) 13
B) 14
C) 15
D) 16
C is correct because starting at 6 and jumping 9 on the number line lands on 15.
2. Ben has 7 books. He borrows 8 more from the library. How many books does he have in all?
A) 13
B) 14
C) 15
D) 16
C is correct because 7 + 8 = 15 books in all.
3. Which number sentence equals 18?
A) 9 + 8
B) 10 + 7
C) 9 + 9
D) 8 + 8
C is correct because 9 + 9 = 18, while A = 17, B = 17, and D = 16.
4. You need to reach 20 on the number line. You are at 13. How many more jumps do you need?
A) 5
B) 6
C) 7
D) 8
C is correct because 20 - 13 = 7 jumps to reach 20.
Part B: Fill in the Missing Number
Use the number line to find the missing number. Write it on the line.
1. 9 + 8 = 17
To find the missing number, subtract 8 from 17: 17 - 8 = 9, so 9 + 8 = 17.
2. 6 + 9 = 15
To find the missing number, subtract 6 from 15: 15 - 6 = 9, so 6 + 9 = 15.
3. 13 + 7 = 20
To find the missing number, subtract 7 from 20: 20 - 7 = 13, so 13 + 7 = 20.
4. 11 + 7 = 18
To find the missing number, subtract 11 from 18: 18 - 11 = 7, so 11 + 7 = 18.
5. 5 + 9 = 14
To find the missing number, subtract 9 from 14: 14 - 9 = 5, so 5 + 9 = 14.