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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 703 · 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. 1.43 − 29 =
  2. 2.22 + 29 =
  3. 3.50 + 29 =
  4. 4.60 + 9 =
  5. 5.36 + 29 =
  6. 6.62 + 9 =
  7. 7.18 + 9 =
  8. 8.30 + 19 =
  9. 9.37 − 19 =
  10. 10.80 + 9 =
  11. 11.51 + 19 =
  12. 12.249 + 99 =
  13. 13.23 − 19 =
  14. 14.52 + 9 =
  15. 15.68 + 19 =
  16. 16.74 + 19 =
  17. 17.33 + 19 =
  18. 18.26 + 9 =
  19. 19.66 − 9 =
  20. 20.58 − 29 =
  21. 21.80 − 19 =
  22. 22.25 + 9 =
  23. 23.47 + 29 =
  24. 24.102 − 29 =
  25. 25.42 − 19 =
  26. 26.445 + 99 =
  27. 27.895 − 99 =
  28. 28.29 + 19 =
  29. 29.71 − 19 =
  30. 30.104 − 29 =
  31. 31.12 + 19 =
  32. 32.16 + 29 =
  33. 33.58 + 9 =
  34. 34.72 − 29 =
  35. 35.79 + 9 =
  36. 36.22 + 19 =
  37. 37.17 − 9 =
  38. 38.25 − 19 =
  39. 39.14 + 9 =
  40. 40.13 + 29 =

Answer key

  1. 14
  2. 51
  3. 79
  4. 69
  5. 65
  6. 71
  7. 27
  8. 49
  9. 18
  10. 89
  11. 70
  12. 348
  13. 4
  14. 61
  15. 87
  16. 93
  17. 52
  18. 35
  19. 57
  20. 29
  21. 61
  22. 34
  23. 76
  24. 73
  25. 23
  26. 544
  27. 796
  28. 48
  29. 52
  30. 75
  31. 31
  32. 45
  33. 67
  34. 43
  35. 88
  36. 41
  37. 8
  38. 6
  39. 23
  40. 42

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