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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 844 · 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. 1.494 − 284 =
  2. 2.831 − 306 =
  3. 3.698 − 318 =
  4. 4.787 + 146 =
  5. 5.768 − 397 =
  6. 6.430 + 499 =
  7. 7.577 + 246 =
  8. 8.264 + 412 =
  9. 9.151 + 226 =
  10. 10.973 − 674 =
  11. 11.500 − 328 =
  12. 12.633 − 151 =
  13. 13.177 + 559 =
  14. 14.414 − 284 =
  15. 15.294 + 179 =
  16. 16.550 − 162 =
  17. 17.498 + 494 =
  18. 18.900 − 115 =
  19. 19.605 + 658 =
  20. 20.638 − 473 =
  21. 21.873 − 495 =
  22. 22.956 − 659 =
  23. 23.555 − 448 =
  24. 24.722 − 469 =
  25. 25.126 + 248 =
  26. 26.610 + 169 =
  27. 27.759 − 137 =
  28. 28.201 + 623 =
  29. 29.172 + 427 =
  30. 30.124 + 623 =
  31. 31.171 + 245 =
  32. 32.849 − 614 =
  33. 33.775 − 351 =
  34. 34.705 − 139 =
  35. 35.165 + 463 =
  36. 36.911 − 385 =
  37. 37.578 − 407 =
  38. 38.481 − 331 =
  39. 39.424 − 291 =
  40. 40.680 + 587 =

Answer key

  1. 210
  2. 525
  3. 380
  4. 933
  5. 371
  6. 929
  7. 823
  8. 676
  9. 377
  10. 299
  11. 172
  12. 482
  13. 736
  14. 130
  15. 473
  16. 388
  17. 992
  18. 785
  19. 1263
  20. 165
  21. 378
  22. 297
  23. 107
  24. 253
  25. 374
  26. 779
  27. 622
  28. 824
  29. 599
  30. 747
  31. 416
  32. 235
  33. 424
  34. 566
  35. 628
  36. 526
  37. 171
  38. 150
  39. 133
  40. 1267

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