Addition Within 20 — Answer Key
Part A: Add Using the Number Line
Start at the first number and count on. Write each sum.
6
+5
11
7
+4
11
8
+3
11
5
+7
12
9
+4
13
6
+8
14
7
+6
13
8
+7
15
Part B: Fill in the Blank
Read each sentence. Write the missing number on the line.
1. 7 + 5 = 12
Start at 7 on the number line and jump 5 spaces to land on 12.
2. 6 + 7 = 13
To find the missing number, subtract 6 from 13: 13 - 6 = 7, so 6 + 7 = 13.
3. If you start at 8 on the number line and jump 5, you land on 13.
Start at 8 on the number line and count 5 jumps forward to land on 13.
4. 9 + 6 = 15
Start at 9 on the number line and jump 6 spaces to land on 15.
5. 6 + 8 = 14
To find the missing number, subtract 8 from 14: 14 - 8 = 6, so 6 + 8 = 14.
Part C: True or False
Write True or False for each statement.
1. 8 + 6 = 14.
True False
This is true because 8 + 6 = 14.
2. On a number line, 7 + 5 lands on 13.
True False
This is false because 7 + 5 = 12, not 13.
3. 6 + 9 is the same as 9 + 6.
True False
This is true because you can add numbers in any order and still get the same answer: both equal 15.