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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 715 · 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. 1.52 − 9 =
  2. 2.88 − 19 =
  3. 3.80 − 29 =
  4. 4.721 + 99 =
  5. 5.486 − 99 =
  6. 6.87 − 29 =
  7. 7.15 + 9 =
  8. 8.105 − 29 =
  9. 9.283 − 99 =
  10. 10.169 − 99 =
  11. 11.39 − 19 =
  12. 12.64 + 29 =
  13. 13.627 + 99 =
  14. 14.90 − 19 =
  15. 15.62 − 9 =
  16. 16.13 + 19 =
  17. 17.23 + 29 =
  18. 18.28 + 29 =
  19. 19.48 − 29 =
  20. 20.510 + 99 =
  21. 21.707 + 99 =
  22. 22.245 − 99 =
  23. 23.28 + 19 =
  24. 24.23 − 9 =
  25. 25.32 + 9 =
  26. 26.29 + 9 =
  27. 27.621 + 99 =
  28. 28.618 − 99 =
  29. 29.49 + 29 =
  30. 30.94 − 19 =
  31. 31.43 − 19 =
  32. 32.63 + 19 =
  33. 33.52 + 29 =
  34. 34.64 − 19 =
  35. 35.80 + 29 =
  36. 36.30 + 9 =
  37. 37.55 + 29 =
  38. 38.38 − 29 =
  39. 39.581 + 99 =
  40. 40.68 + 19 =

Answer key

  1. 43
  2. 69
  3. 51
  4. 820
  5. 387
  6. 58
  7. 24
  8. 76
  9. 184
  10. 70
  11. 20
  12. 93
  13. 726
  14. 71
  15. 53
  16. 32
  17. 52
  18. 57
  19. 19
  20. 609
  21. 806
  22. 146
  23. 47
  24. 14
  25. 41
  26. 38
  27. 720
  28. 519
  29. 78
  30. 75
  31. 24
  32. 82
  33. 81
  34. 45
  35. 109
  36. 39
  37. 84
  38. 9
  39. 680
  40. 87

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