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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 835 · 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. 1.20 + 9 =
  2. 2.85 − 29 =
  3. 3.61 − 29 =
  4. 4.183 − 99 =
  5. 5.84 − 9 =
  6. 6.79 + 29 =
  7. 7.66 + 29 =
  8. 8.610 + 99 =
  9. 9.269 + 99 =
  10. 10.17 + 29 =
  11. 11.51 + 19 =
  12. 12.64 − 9 =
  13. 13.676 − 99 =
  14. 14.48 − 29 =
  15. 15.55 + 29 =
  16. 16.29 + 9 =
  17. 17.78 + 9 =
  18. 18.42 − 19 =
  19. 19.52 − 9 =
  20. 20.14 + 19 =
  21. 21.49 − 29 =
  22. 22.83 − 9 =
  23. 23.37 − 19 =
  24. 24.49 + 9 =
  25. 25.24 − 9 =
  26. 26.591 + 99 =
  27. 27.107 + 99 =
  28. 28.31 + 19 =
  29. 29.51 − 29 =
  30. 30.55 − 19 =
  31. 31.752 + 99 =
  32. 32.596 + 99 =
  33. 33.333 − 99 =
  34. 34.85 − 9 =
  35. 35.19 + 19 =
  36. 36.585 + 99 =
  37. 37.22 − 19 =
  38. 38.38 + 29 =
  39. 39.59 + 9 =
  40. 40.22 + 29 =

Answer key

  1. 29
  2. 56
  3. 32
  4. 84
  5. 75
  6. 108
  7. 95
  8. 709
  9. 368
  10. 46
  11. 70
  12. 55
  13. 577
  14. 19
  15. 84
  16. 38
  17. 87
  18. 23
  19. 43
  20. 33
  21. 20
  22. 74
  23. 18
  24. 58
  25. 15
  26. 690
  27. 206
  28. 50
  29. 22
  30. 36
  31. 851
  32. 695
  33. 234
  34. 76
  35. 38
  36. 684
  37. 3
  38. 67
  39. 68
  40. 51

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