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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 292 · 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 − 19 =
  2. 2.61 + 19 =
  3. 3.44 + 9 =
  4. 4.80 − 9 =
  5. 5.57 + 9 =
  6. 6.13 + 29 =
  7. 7.242 − 99 =
  8. 8.743 + 99 =
  9. 9.67 − 9 =
  10. 10.41 + 9 =
  11. 11.81 − 19 =
  12. 12.410 + 99 =
  13. 13.32 + 9 =
  14. 14.69 − 9 =
  15. 15.92 − 19 =
  16. 16.333 − 99 =
  17. 17.96 − 19 =
  18. 18.72 + 19 =
  19. 19.49 − 29 =
  20. 20.43 + 19 =
  21. 21.61 − 29 =
  22. 22.49 + 29 =
  23. 23.88 − 29 =
  24. 24.630 + 99 =
  25. 25.43 − 29 =
  26. 26.39 − 19 =
  27. 27.87 − 9 =
  28. 28.39 + 19 =
  29. 29.20 + 29 =
  30. 30.168 − 99 =
  31. 31.428 − 99 =
  32. 32.54 + 9 =
  33. 33.17 + 19 =
  34. 34.88 − 9 =
  35. 35.59 − 29 =
  36. 36.91 − 19 =
  37. 37.56 − 29 =
  38. 38.328 + 99 =
  39. 39.226 − 99 =
  40. 40.74 + 9 =

Answer key

  1. 14
  2. 80
  3. 53
  4. 71
  5. 66
  6. 42
  7. 143
  8. 842
  9. 58
  10. 50
  11. 62
  12. 509
  13. 41
  14. 60
  15. 73
  16. 234
  17. 77
  18. 91
  19. 20
  20. 62
  21. 32
  22. 78
  23. 59
  24. 729
  25. 14
  26. 20
  27. 78
  28. 58
  29. 49
  30. 69
  31. 329
  32. 63
  33. 36
  34. 79
  35. 30
  36. 72
  37. 27
  38. 427
  39. 127
  40. 83

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