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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 660 · 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. 1.33 + 9 =
  2. 2.69 + 29 =
  3. 3.72 + 19 =
  4. 4.64 − 19 =
  5. 5.24 + 29 =
  6. 6.50 + 19 =
  7. 7.70 + 9 =
  8. 8.55 − 29 =
  9. 9.20 + 29 =
  10. 10.76 + 29 =
  11. 11.245 + 99 =
  12. 12.60 + 29 =
  13. 13.244 − 99 =
  14. 14.17 − 9 =
  15. 15.56 − 9 =
  16. 16.61 − 29 =
  17. 17.30 + 19 =
  18. 18.75 − 9 =
  19. 19.37 + 9 =
  20. 20.53 + 29 =
  21. 21.92 − 19 =
  22. 22.62 + 9 =
  23. 23.55 + 29 =
  24. 24.76 − 29 =
  25. 25.50 + 9 =
  26. 26.64 − 29 =
  27. 27.60 + 19 =
  28. 28.87 − 29 =
  29. 29.28 − 9 =
  30. 30.33 + 29 =
  31. 31.302 − 99 =
  32. 32.575 + 99 =
  33. 33.52 + 9 =
  34. 34.33 + 19 =
  35. 35.590 − 99 =
  36. 36.44 + 9 =
  37. 37.65 + 29 =
  38. 38.799 − 99 =
  39. 39.104 − 29 =
  40. 40.51 − 29 =

Answer key

  1. 42
  2. 98
  3. 91
  4. 45
  5. 53
  6. 69
  7. 79
  8. 26
  9. 49
  10. 105
  11. 344
  12. 89
  13. 145
  14. 8
  15. 47
  16. 32
  17. 49
  18. 66
  19. 46
  20. 82
  21. 73
  22. 71
  23. 84
  24. 47
  25. 59
  26. 35
  27. 79
  28. 58
  29. 19
  30. 62
  31. 203
  32. 674
  33. 61
  34. 52
  35. 491
  36. 53
  37. 94
  38. 700
  39. 75
  40. 22

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