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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 301 · 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. 1.649 + 99 =
  2. 2.57 + 29 =
  3. 3.434 − 99 =
  4. 4.66 + 29 =
  5. 5.213 + 99 =
  6. 6.99 − 19 =
  7. 7.15 + 29 =
  8. 8.52 + 9 =
  9. 9.210 − 99 =
  10. 10.315 + 99 =
  11. 11.19 + 9 =
  12. 12.61 − 19 =
  13. 13.61 + 29 =
  14. 14.50 + 19 =
  15. 15.82 − 9 =
  16. 16.27 + 19 =
  17. 17.628 − 99 =
  18. 18.26 + 29 =
  19. 19.67 + 9 =
  20. 20.485 − 99 =
  21. 21.83 − 19 =
  22. 22.28 − 19 =
  23. 23.16 + 29 =
  24. 24.156 − 99 =
  25. 25.572 + 99 =
  26. 26.36 + 29 =
  27. 27.52 − 29 =
  28. 28.394 + 99 =
  29. 29.738 + 99 =
  30. 30.64 + 9 =
  31. 31.48 − 29 =
  32. 32.42 + 19 =
  33. 33.77 − 19 =
  34. 34.60 + 29 =
  35. 35.483 + 99 =
  36. 36.88 − 29 =
  37. 37.635 − 99 =
  38. 38.27 − 9 =
  39. 39.57 − 9 =
  40. 40.48 − 19 =

Answer key

  1. 748
  2. 86
  3. 335
  4. 95
  5. 312
  6. 80
  7. 44
  8. 61
  9. 111
  10. 414
  11. 28
  12. 42
  13. 90
  14. 69
  15. 73
  16. 46
  17. 529
  18. 55
  19. 76
  20. 386
  21. 64
  22. 9
  23. 45
  24. 57
  25. 671
  26. 65
  27. 23
  28. 493
  29. 837
  30. 73
  31. 19
  32. 61
  33. 58
  34. 89
  35. 582
  36. 59
  37. 536
  38. 18
  39. 48
  40. 29

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