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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 550 · 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. 1.886 − 197 =
  2. 2.215 − 178 =
  3. 3.374 − 297 =
  4. 4.520 − 327 =
  5. 5.488 − 438 =
  6. 6.868 − 797 =
  7. 7.967 − 399 =
  8. 8.868 − 549 =
  9. 9.813 − 257 =
  10. 10.387 − 138 =
  11. 11.766 − 697 =
  12. 12.419 − 328 =
  13. 13.157 − 119 =
  14. 14.840 − 199 =
  15. 15.840 − 298 =
  16. 16.744 − 639 =
  17. 17.321 − 118 =
  18. 18.797 − 499 =
  19. 19.665 − 499 =
  20. 20.281 − 239 =
  21. 21.953 − 198 =
  22. 22.503 − 398 =
  23. 23.362 − 299 =
  24. 24.991 − 399 =
  25. 25.671 − 509 =
  26. 26.919 − 439 =
  27. 27.633 − 117 =
  28. 28.717 − 697 =
  29. 29.663 − 398 =
  30. 30.711 − 509 =
  31. 31.629 − 597 =
  32. 32.541 − 499 =
  33. 33.885 − 197 =
  34. 34.829 − 407 =
  35. 35.421 − 199 =
  36. 36.814 − 667 =
  37. 37.884 − 797 =
  38. 38.295 − 239 =
  39. 39.872 − 297 =
  40. 40.983 − 599 =

Answer key

  1. 689
  2. 37
  3. 77
  4. 193
  5. 50
  6. 71
  7. 568
  8. 319
  9. 556
  10. 249
  11. 69
  12. 91
  13. 38
  14. 641
  15. 542
  16. 105
  17. 203
  18. 298
  19. 166
  20. 42
  21. 755
  22. 105
  23. 63
  24. 592
  25. 162
  26. 480
  27. 516
  28. 20
  29. 265
  30. 202
  31. 32
  32. 42
  33. 688
  34. 422
  35. 222
  36. 147
  37. 87
  38. 56
  39. 575
  40. 384

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