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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 604 · 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. 1.831 − 99 =
  2. 2.61 + 9 =
  3. 3.62 + 29 =
  4. 4.65 − 19 =
  5. 5.26 + 19 =
  6. 6.338 + 99 =
  7. 7.27 + 9 =
  8. 8.73 + 29 =
  9. 9.510 + 99 =
  10. 10.630 − 99 =
  11. 11.74 + 19 =
  12. 12.580 + 99 =
  13. 13.58 + 19 =
  14. 14.39 − 9 =
  15. 15.43 + 9 =
  16. 16.47 + 19 =
  17. 17.49 − 29 =
  18. 18.342 + 99 =
  19. 19.50 − 9 =
  20. 20.41 + 19 =
  21. 21.74 + 9 =
  22. 22.67 + 29 =
  23. 23.62 + 9 =
  24. 24.39 + 19 =
  25. 25.266 + 99 =
  26. 26.753 − 99 =
  27. 27.39 + 9 =
  28. 28.14 + 9 =
  29. 29.441 + 99 =
  30. 30.44 − 19 =
  31. 31.32 + 29 =
  32. 32.57 − 9 =
  33. 33.23 − 9 =
  34. 34.23 − 19 =
  35. 35.70 + 19 =
  36. 36.71 + 9 =
  37. 37.107 + 99 =
  38. 38.660 − 99 =
  39. 39.31 − 9 =
  40. 40.52 − 19 =

Answer key

  1. 732
  2. 70
  3. 91
  4. 46
  5. 45
  6. 437
  7. 36
  8. 102
  9. 609
  10. 531
  11. 93
  12. 679
  13. 77
  14. 30
  15. 52
  16. 66
  17. 20
  18. 441
  19. 41
  20. 60
  21. 83
  22. 96
  23. 71
  24. 58
  25. 365
  26. 654
  27. 48
  28. 23
  29. 540
  30. 25
  31. 61
  32. 48
  33. 14
  34. 4
  35. 89
  36. 80
  37. 206
  38. 561
  39. 22
  40. 33

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