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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 990 · 40 questions
TalentJR

How to do it in your head (Round up, add back): Round the number you take away up to the next ten or hundred: 297 → 300 (3 too many). Take away the round number. Add back the extra, because you took away too much.

NameDateTime takenScore ___ / 40
  1. 1.706 − 597 =
  2. 2.659 − 639 =
  3. 3.500 − 387 =
  4. 4.322 − 217 =
  5. 5.763 − 458 =
  6. 6.994 − 798 =
  7. 7.963 − 507 =
  8. 8.849 − 599 =
  9. 9.930 − 497 =
  10. 10.765 − 297 =
  11. 11.510 − 259 =
  12. 12.635 − 379 =
  13. 13.958 − 797 =
  14. 14.983 − 697 =
  15. 15.351 − 308 =
  16. 16.537 − 298 =
  17. 17.523 − 159 =
  18. 18.625 − 497 =
  19. 19.905 − 497 =
  20. 20.688 − 498 =
  21. 21.359 − 198 =
  22. 22.821 − 598 =
  23. 23.639 − 599 =
  24. 24.246 − 229 =
  25. 25.793 − 399 =
  26. 26.815 − 298 =
  27. 27.643 − 118 =
  28. 28.302 − 197 =
  29. 29.926 − 509 =
  30. 30.633 − 499 =
  31. 31.723 − 579 =
  32. 32.950 − 799 =
  33. 33.419 − 319 =
  34. 34.669 − 519 =
  35. 35.485 − 259 =
  36. 36.521 − 228 =
  37. 37.541 − 198 =
  38. 38.313 − 199 =
  39. 39.333 − 299 =
  40. 40.834 − 599 =

Answer key

  1. 109
  2. 20
  3. 113
  4. 105
  5. 305
  6. 196
  7. 456
  8. 250
  9. 433
  10. 468
  11. 251
  12. 256
  13. 161
  14. 286
  15. 43
  16. 239
  17. 364
  18. 128
  19. 408
  20. 190
  21. 161
  22. 223
  23. 40
  24. 17
  25. 394
  26. 517
  27. 525
  28. 105
  29. 417
  30. 134
  31. 144
  32. 151
  33. 100
  34. 150
  35. 226
  36. 293
  37. 343
  38. 114
  39. 34
  40. 235

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