3-digit addition problems
Thirty problems adding a two-digit number to a three-digit one: the hardest addition in the daily sprint.
30 problems · answer key ·
Problems
Name: ________________ Time: ________
- 352 + 66 =
- 438 + 34 =
- 446 + 93 =
- 249 + 81 =
- 417 + 97 =
- 407 + 12 =
- 300 + 87 =
- 313 + 35 =
- 237 + 88 =
- 248 + 60 =
- 401 + 99 =
- 446 + 72 =
- 141 + 89 =
- 171 + 92 =
- 127 + 24 =
- 206 + 79 =
- 121 + 54 =
- 366 + 53 =
- 145 + 15 =
- 421 + 37 =
- 199 + 12 =
- 279 + 97 =
- 154 + 69 =
- 334 + 80 =
- 124 + 56 =
- 363 + 31 =
- 102 + 22 =
- 454 + 86 =
- 111 + 77 =
- 307 + 63 =
How to do them fast
Keep the big number whole and add the small one in two steps, tens and then ones.
347 + 68 = 415
347 + 60 = 407 → 407 + 8 = 415
Close to 100? Add the hundred and take the difference back.
265 + 97 = 362
265 + 100 = 365 → 365 − 3 = 362
Around 3 seconds each is good going; under 2 is fast. More methods are in the mental math tricks.
Answer key
- 352 + 66 = 418
- 438 + 34 = 472
- 446 + 93 = 539
- 249 + 81 = 330
- 417 + 97 = 514
- 407 + 12 = 419
- 300 + 87 = 387
- 313 + 35 = 348
- 237 + 88 = 325
- 248 + 60 = 308
- 401 + 99 = 500
- 446 + 72 = 518
- 141 + 89 = 230
- 171 + 92 = 263
- 127 + 24 = 151
- 206 + 79 = 285
- 121 + 54 = 175
- 366 + 53 = 419
- 145 + 15 = 160
- 421 + 37 = 458
- 199 + 12 = 211
- 279 + 97 = 376
- 154 + 69 = 223
- 334 + 80 = 414
- 124 + 56 = 180
- 363 + 31 = 394
- 102 + 22 = 124
- 454 + 86 = 540
- 111 + 77 = 188
- 307 + 63 = 370