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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 182 · 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. 1.273 + 299 =
  2. 2.363 + 215 =
  3. 3.551 + 246 =
  4. 4.323 + 151 =
  5. 5.629 + 244 =
  6. 6.574 − 401 =
  7. 7.717 − 431 =
  8. 8.213 + 227 =
  9. 9.763 + 447 =
  10. 10.563 + 541 =
  11. 11.481 + 299 =
  12. 12.495 + 242 =
  13. 13.176 + 278 =
  14. 14.666 − 114 =
  15. 15.484 − 249 =
  16. 16.688 + 518 =
  17. 17.468 − 166 =
  18. 18.701 + 372 =
  19. 19.589 + 586 =
  20. 20.467 − 283 =
  21. 21.807 − 595 =
  22. 22.539 − 142 =
  23. 23.728 − 232 =
  24. 24.789 + 451 =
  25. 25.158 + 121 =
  26. 26.430 + 249 =
  27. 27.289 + 146 =
  28. 28.153 + 619 =
  29. 29.273 + 311 =
  30. 30.789 + 261 =
  31. 31.757 + 293 =
  32. 32.875 − 471 =
  33. 33.606 − 221 =
  34. 34.844 − 535 =
  35. 35.475 − 287 =
  36. 36.235 + 426 =
  37. 37.424 + 377 =
  38. 38.287 + 585 =
  39. 39.618 + 542 =
  40. 40.245 + 672 =

Answer key

  1. 572
  2. 578
  3. 797
  4. 474
  5. 873
  6. 173
  7. 286
  8. 440
  9. 1210
  10. 1104
  11. 780
  12. 737
  13. 454
  14. 552
  15. 235
  16. 1206
  17. 302
  18. 1073
  19. 1175
  20. 184
  21. 212
  22. 397
  23. 496
  24. 1240
  25. 279
  26. 679
  27. 435
  28. 772
  29. 584
  30. 1050
  31. 1050
  32. 404
  33. 385
  34. 309
  35. 188
  36. 661
  37. 801
  38. 872
  39. 1160
  40. 917

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