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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 524 · 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. 1.49 + 9 =
  2. 2.50 + 19 =
  3. 3.85 − 29 =
  4. 4.65 − 29 =
  5. 5.19 + 29 =
  6. 6.52 − 29 =
  7. 7.590 − 99 =
  8. 8.53 − 29 =
  9. 9.13 + 29 =
  10. 10.668 − 99 =
  11. 11.16 + 29 =
  12. 12.13 − 9 =
  13. 13.79 + 29 =
  14. 14.36 + 19 =
  15. 15.237 + 99 =
  16. 16.72 + 19 =
  17. 17.38 + 9 =
  18. 18.502 − 99 =
  19. 19.30 + 9 =
  20. 20.49 − 19 =
  21. 21.15 + 9 =
  22. 22.44 − 19 =
  23. 23.81 − 9 =
  24. 24.259 − 99 =
  25. 25.22 + 19 =
  26. 26.68 − 19 =
  27. 27.28 + 19 =
  28. 28.26 − 9 =
  29. 29.57 + 29 =
  30. 30.65 + 19 =
  31. 31.31 + 9 =
  32. 32.71 − 29 =
  33. 33.40 − 9 =
  34. 34.74 + 9 =
  35. 35.32 − 9 =
  36. 36.43 + 29 =
  37. 37.43 + 9 =
  38. 38.111 + 99 =
  39. 39.80 + 9 =
  40. 40.39 − 9 =

Answer key

  1. 58
  2. 69
  3. 56
  4. 36
  5. 48
  6. 23
  7. 491
  8. 24
  9. 42
  10. 569
  11. 45
  12. 4
  13. 108
  14. 55
  15. 336
  16. 91
  17. 47
  18. 403
  19. 39
  20. 30
  21. 24
  22. 25
  23. 72
  24. 160
  25. 41
  26. 49
  27. 47
  28. 17
  29. 86
  30. 84
  31. 40
  32. 42
  33. 31
  34. 83
  35. 23
  36. 72
  37. 52
  38. 210
  39. 89
  40. 30

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