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Adding 9, 19 and 99 Mental Maths Worksheet

Mental maths lesson 4: Add and take away 9, 19 and 99 · Set 704 · 40 questions
TalentJR

How to do it in your head (Round and adjust): Add 9, 19, 99: add 10, 20, 100, then take 1 away. Take away 9, 19, 99: take away 10, 20, 100, then add 1 back. Ask yourself: did I use too much or too little?

NameDateTime takenScore ___ / 40
  1. 1.591 − 99 =
  2. 2.24 + 29 =
  3. 3.88 − 19 =
  4. 4.362 − 99 =
  5. 5.13 − 9 =
  6. 6.23 + 29 =
  7. 7.57 + 9 =
  8. 8.20 + 9 =
  9. 9.48 + 29 =
  10. 10.38 − 9 =
  11. 11.397 + 99 =
  12. 12.27 − 9 =
  13. 13.278 + 99 =
  14. 14.20 − 9 =
  15. 15.737 − 99 =
  16. 16.46 − 9 =
  17. 17.48 − 19 =
  18. 18.38 + 29 =
  19. 19.36 − 9 =
  20. 20.303 + 99 =
  21. 21.72 + 29 =
  22. 22.790 − 99 =
  23. 23.493 + 99 =
  24. 24.77 + 9 =
  25. 25.87 − 9 =
  26. 26.101 − 29 =
  27. 27.54 + 19 =
  28. 28.27 + 9 =
  29. 29.71 − 9 =
  30. 30.36 − 19 =
  31. 31.225 − 99 =
  32. 32.363 − 99 =
  33. 33.429 + 99 =
  34. 34.49 + 9 =
  35. 35.608 + 99 =
  36. 36.43 − 19 =
  37. 37.12 + 29 =
  38. 38.69 − 19 =
  39. 39.33 + 19 =
  40. 40.163 − 99 =

Answer key

  1. 492
  2. 53
  3. 69
  4. 263
  5. 4
  6. 52
  7. 66
  8. 29
  9. 77
  10. 29
  11. 496
  12. 18
  13. 377
  14. 11
  15. 638
  16. 37
  17. 29
  18. 67
  19. 27
  20. 402
  21. 101
  22. 691
  23. 592
  24. 86
  25. 78
  26. 72
  27. 73
  28. 36
  29. 62
  30. 17
  31. 126
  32. 264
  33. 528
  34. 58
  35. 707
  36. 24
  37. 41
  38. 50
  39. 52
  40. 64

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