← Subtract by rounding up and adding back lesson New set →

Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 847 · 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. 1.968 − 668 =
  2. 2.692 − 649 =
  3. 3.396 − 379 =
  4. 4.573 − 297 =
  5. 5.966 − 498 =
  6. 6.465 − 347 =
  7. 7.917 − 388 =
  8. 8.947 − 298 =
  9. 9.637 − 237 =
  10. 10.845 − 199 =
  11. 11.543 − 298 =
  12. 12.453 − 338 =
  13. 13.441 − 317 =
  14. 14.564 − 498 =
  15. 15.707 − 399 =
  16. 16.831 − 599 =
  17. 17.927 − 499 =
  18. 18.805 − 598 =
  19. 19.219 − 189 =
  20. 20.736 − 127 =
  21. 21.760 − 667 =
  22. 22.615 − 398 =
  23. 23.365 − 198 =
  24. 24.751 − 297 =
  25. 25.415 − 299 =
  26. 26.425 − 279 =
  27. 27.595 − 479 =
  28. 28.388 − 299 =
  29. 29.773 − 199 =
  30. 30.901 − 697 =
  31. 31.366 − 299 =
  32. 32.758 − 599 =
  33. 33.320 − 288 =
  34. 34.959 − 398 =
  35. 35.755 − 597 =
  36. 36.679 − 399 =
  37. 37.650 − 447 =
  38. 38.998 − 599 =
  39. 39.420 − 297 =
  40. 40.245 − 149 =

Answer key

  1. 300
  2. 43
  3. 17
  4. 276
  5. 468
  6. 118
  7. 529
  8. 649
  9. 400
  10. 646
  11. 245
  12. 115
  13. 124
  14. 66
  15. 308
  16. 232
  17. 428
  18. 207
  19. 30
  20. 609
  21. 93
  22. 217
  23. 167
  24. 454
  25. 116
  26. 146
  27. 116
  28. 89
  29. 574
  30. 204
  31. 67
  32. 159
  33. 32
  34. 561
  35. 158
  36. 280
  37. 203
  38. 399
  39. 123
  40. 96

Free mental maths lessons, practice and worksheets at talentjr.in/mental-maths