Add & Subtract Within 1000 — Answer Key
Part A: Fill in the Blank
Write the missing word or number on each line.
1. 245 + 137 = 245 + 100 + 30 + 7
137 = 100 + 30 + 7, so the missing piece is 7.
2. 318 + 204 = 318 + 200 + 4
204 = 200 + 4, so jumping +200 then +4 completes the sum.
3. Start at 460. Jump +100, +20, +5. You land on 585.
460 + 100 = 560, 560 + 20 = 580, 580 + 5 = 585.
4. 562 + 125 = 562 + 100 + 20 + 5
125 = 100 + 20 + 5, so the missing tens jump is 20.
5. Start at 283. Jump +200, +40, +3. You land on 526.
283 + 200 = 483, 483 + 40 = 523, 523 + 3 = 526.
6. 417 + 265 = 417 + 200 + 60 + 5
The ones digit of 265 is 5, so the last jump is 5.
7. 350 + 148 = 350 + 100 + 40 + 8
148 = 100 + 40 + 8, so the hundreds jump is 100.
8. Start at 178. Jump +300, +10, +2. You land on 490.
178 + 300 = 478, 478 + 10 = 488, 488 + 2 = 490.
9. 529 + 163 = 529 + 100 + 60 + 3
163 = 100 + 60 + 3, so the final ones jump is 3.
Part B: Matching
Match each item on the left to the correct answer on the right.
1. Match each item to its correct answer.
236 + 142
→ break into 100+40+2
break into 100+40+2
305 + 218
→ break into 200+10+8
break into 200+10+8
471 + 124
→ break into 100+20+4
break into 100+20+4
158 + 230
→ break into 200+30+0
break into 200+30+0
142=100+40+2, 218=200+10+8, 124=100+20+4, and 230=200+30+0.