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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 787 · 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. 1.585 + 528 =
  2. 2.450 + 621 =
  3. 3.573 + 248 =
  4. 4.867 − 671 =
  5. 5.273 + 188 =
  6. 6.499 − 126 =
  7. 7.666 + 516 =
  8. 8.238 + 194 =
  9. 9.928 − 257 =
  10. 10.505 − 183 =
  11. 11.631 − 193 =
  12. 12.696 − 512 =
  13. 13.449 − 335 =
  14. 14.245 + 431 =
  15. 15.305 + 364 =
  16. 16.476 + 137 =
  17. 17.930 − 681 =
  18. 18.625 + 382 =
  19. 19.160 + 355 =
  20. 20.426 − 126 =
  21. 21.310 + 588 =
  22. 22.277 + 566 =
  23. 23.816 − 443 =
  24. 24.939 − 374 =
  25. 25.533 − 122 =
  26. 26.824 − 561 =
  27. 27.424 + 199 =
  28. 28.186 + 504 =
  29. 29.558 + 668 =
  30. 30.129 + 202 =
  31. 31.730 − 591 =
  32. 32.713 − 492 =
  33. 33.460 + 652 =
  34. 34.888 − 303 =
  35. 35.735 − 168 =
  36. 36.751 + 482 =
  37. 37.529 − 345 =
  38. 38.759 + 128 =
  39. 39.720 − 311 =
  40. 40.738 − 183 =

Answer key

  1. 1113
  2. 1071
  3. 821
  4. 196
  5. 461
  6. 373
  7. 1182
  8. 432
  9. 671
  10. 322
  11. 438
  12. 184
  13. 114
  14. 676
  15. 669
  16. 613
  17. 249
  18. 1007
  19. 515
  20. 300
  21. 898
  22. 843
  23. 373
  24. 565
  25. 411
  26. 263
  27. 623
  28. 690
  29. 1226
  30. 331
  31. 139
  32. 221
  33. 1112
  34. 585
  35. 567
  36. 1233
  37. 184
  38. 887
  39. 409
  40. 555

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