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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 78 · 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. 1.634 + 659 =
  2. 2.963 − 518 =
  3. 3.751 + 253 =
  4. 4.740 − 609 =
  5. 5.687 − 433 =
  6. 6.500 − 243 =
  7. 7.987 − 668 =
  8. 8.181 + 149 =
  9. 9.948 − 683 =
  10. 10.787 + 195 =
  11. 11.754 − 528 =
  12. 12.511 − 351 =
  13. 13.713 + 254 =
  14. 14.352 + 283 =
  15. 15.342 + 613 =
  16. 16.350 + 514 =
  17. 17.678 + 625 =
  18. 18.751 − 487 =
  19. 19.631 − 295 =
  20. 20.784 − 372 =
  21. 21.539 − 146 =
  22. 22.459 + 531 =
  23. 23.129 + 574 =
  24. 24.299 + 281 =
  25. 25.636 − 387 =
  26. 26.500 + 119 =
  27. 27.636 − 271 =
  28. 28.854 − 527 =
  29. 29.920 − 288 =
  30. 30.481 + 535 =
  31. 31.755 + 268 =
  32. 32.356 + 595 =
  33. 33.380 + 241 =
  34. 34.491 − 338 =
  35. 35.330 + 143 =
  36. 36.353 + 533 =
  37. 37.554 − 173 =
  38. 38.781 + 405 =
  39. 39.674 − 318 =
  40. 40.632 + 151 =

Answer key

  1. 1293
  2. 445
  3. 1004
  4. 131
  5. 254
  6. 257
  7. 319
  8. 330
  9. 265
  10. 982
  11. 226
  12. 160
  13. 967
  14. 635
  15. 955
  16. 864
  17. 1303
  18. 264
  19. 336
  20. 412
  21. 393
  22. 990
  23. 703
  24. 580
  25. 249
  26. 619
  27. 365
  28. 327
  29. 632
  30. 1016
  31. 1023
  32. 951
  33. 621
  34. 153
  35. 473
  36. 886
  37. 381
  38. 1186
  39. 356
  40. 783

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