Addition Within 20 (Number Lines) — Answer Key
Part A: Fill in the Blank
Write the missing word or number on each line.
1. 6 + 7 = 13
Start at 6 on the number line and jump 7 spaces forward to reach 13.
2. 8 + 9 = 17
From 8, count up 9 more spaces on the number line. You pass through 10 and land on 17.
3. 5 + 8 = 13
Start at 5 and hop forward 8 times: 6, 7, 8, 9, 10, 11, 12, 13. You end at 13.
4. 9 + 5 = 14
From 9, jump 5 spaces ahead on the number line to reach 14. You only need 1 jump to get to 10, then 4 more.
5. 7 + 9 = 16
Start at 7 and count forward 9 spaces. You pass 10 and keep going until you reach 16.
6. 4 + 8 = 12
From 4, hop 8 spaces forward on the number line to land on 12.
7. 6 + 9 = 15
Start at 6 and jump 9 spaces ahead. You go past 10 and stop at 15.
8. 8 + 4 = 12
Begin at 8 and count forward 4: 9, 10, 11, 12. The answer is 12.
9. 7 + 7 = 14
7 + 7 is a double. Two groups of 7 equal 14. You can check by jumping 7 spaces from 7 on the number line.
Part B: Matching
Match each item on the left to the correct answer on the right.
1. Match each item to its correct answer.
9 + 8
→ 17
11
6 + 6
→ 12
12
7 + 4
→ 11
15
8 + 7
→ 15
17
Each problem matches its sum: 9 + 8 = 17, 6 + 6 = 12 (a double), 7 + 4 = 11, and 8 + 7 = 15. Use the number line to check each one.