← 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 240 · 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. 1.345 − 308 =
  2. 2.737 − 297 =
  3. 3.221 − 157 =
  4. 4.950 − 697 =
  5. 5.454 − 428 =
  6. 6.382 − 198 =
  7. 7.661 − 567 =
  8. 8.810 − 239 =
  9. 9.956 − 437 =
  10. 10.722 − 319 =
  11. 11.410 − 297 =
  12. 12.866 − 519 =
  13. 13.841 − 699 =
  14. 14.707 − 297 =
  15. 15.481 − 309 =
  16. 16.608 − 298 =
  17. 17.463 − 408 =
  18. 18.830 − 299 =
  19. 19.748 − 697 =
  20. 20.767 − 398 =
  21. 21.922 − 798 =
  22. 22.905 − 449 =
  23. 23.942 − 349 =
  24. 24.785 − 197 =
  25. 25.677 − 598 =
  26. 26.872 − 799 =
  27. 27.644 − 198 =
  28. 28.707 − 397 =
  29. 29.716 − 499 =
  30. 30.177 − 159 =
  31. 31.840 − 799 =
  32. 32.910 − 599 =
  33. 33.173 − 118 =
  34. 34.607 − 297 =
  35. 35.796 − 618 =
  36. 36.874 − 648 =
  37. 37.512 − 197 =
  38. 38.758 − 518 =
  39. 39.465 − 129 =
  40. 40.750 − 259 =

Answer key

  1. 37
  2. 440
  3. 64
  4. 253
  5. 26
  6. 184
  7. 94
  8. 571
  9. 519
  10. 403
  11. 113
  12. 347
  13. 142
  14. 410
  15. 172
  16. 310
  17. 55
  18. 531
  19. 51
  20. 369
  21. 124
  22. 456
  23. 593
  24. 588
  25. 79
  26. 73
  27. 446
  28. 310
  29. 217
  30. 18
  31. 41
  32. 311
  33. 55
  34. 310
  35. 178
  36. 226
  37. 315
  38. 240
  39. 336
  40. 491

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