Add & Subtract Within 1000 — Answer Key
Part A: Fill in the Blank
Write the missing word or number on each line.
1. 232 + 268 = 500
500 - 232 = 268, so 232 + 268 = 500.
2. 145 + 255 = 400
400 - 145 = 255, so the missing addend is 255.
3. 310 + 290 = 600
600 - 310 = 290, so 310 + 290 = 600.
4. 278 + 172 = 450
450 - 278 = 172, so 278 + 172 = 450.
5. 425 + 375 = 800
800 - 425 = 375, so 425 + 375 = 800.
6. 150 + 175 = 325
325 - 150 = 175, so the missing addend is 175.
7. 206 + 344 = 550
550 - 206 = 344, so 206 + 344 = 550.
8. 482 + 218 = 700
700 - 482 = 218, giving the missing addend.
9. 360 + 540 = 900
900 - 360 = 540, so 360 + 540 = 900.
Part B: Matching
Match each item on the left to the correct answer on the right.
1. Match each item to its correct answer.
215 + __ = 400
→ 185
185
330 + __ = 650
→ 320
320
145 + __ = 500
→ 355
355
260 + __ = 700
→ 440
440
400-215=185, 650-330=320, 500-145=355, and 700-260=440, so the equations match.