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3-Digit Mental Addition and Subtraction Worksheet

Mental maths lesson 20: Add and subtract 3-digit numbers left to right · Set 990 · 40 questions
TalentJR

How to do it in your head (Hundreds first): Keep the first number as it is and split the second into hundreds, tens and ones. Add (or take away) the hundreds first, then the tens. Finish with the ones — bridge through a ten if you need to.

NameDateTime takenScore ___ / 40
  1. 1.552 + 136 =
  2. 2.659 + 155 =
  3. 3.345 + 235 =
  4. 4.214 + 464 =
  5. 5.826 − 726 =
  6. 6.612 − 341 =
  7. 7.785 − 272 =
  8. 8.889 − 719 =
  9. 9.577 + 114 =
  10. 10.850 − 126 =
  11. 11.301 + 245 =
  12. 12.441 − 149 =
  13. 13.131 + 179 =
  14. 14.695 + 238 =
  15. 15.210 + 132 =
  16. 16.155 + 225 =
  17. 17.669 − 289 =
  18. 18.572 − 331 =
  19. 19.516 + 261 =
  20. 20.823 − 589 =
  21. 21.243 + 607 =
  22. 22.596 − 451 =
  23. 23.622 − 321 =
  24. 24.766 + 431 =
  25. 25.846 − 639 =
  26. 26.684 − 491 =
  27. 27.658 − 216 =
  28. 28.934 − 291 =
  29. 29.734 + 559 =
  30. 30.666 + 251 =
  31. 31.587 + 283 =
  32. 32.671 + 394 =
  33. 33.672 + 501 =
  34. 34.505 − 368 =
  35. 35.564 − 454 =
  36. 36.955 − 504 =
  37. 37.246 + 602 =
  38. 38.336 + 264 =
  39. 39.129 + 277 =
  40. 40.125 + 623 =

Answer key

  1. 688
  2. 814
  3. 580
  4. 678
  5. 100
  6. 271
  7. 513
  8. 170
  9. 691
  10. 724
  11. 546
  12. 292
  13. 310
  14. 933
  15. 342
  16. 380
  17. 380
  18. 241
  19. 777
  20. 234
  21. 850
  22. 145
  23. 301
  24. 1197
  25. 207
  26. 193
  27. 442
  28. 643
  29. 1293
  30. 917
  31. 870
  32. 1065
  33. 1173
  34. 137
  35. 110
  36. 451
  37. 848
  38. 600
  39. 406
  40. 748

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