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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 185 · 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. 1.29 + 9 =
  2. 2.28 − 19 =
  3. 3.35 − 29 =
  4. 4.66 + 19 =
  5. 5.504 + 99 =
  6. 6.108 − 29 =
  7. 7.31 + 9 =
  8. 8.59 − 9 =
  9. 9.539 + 99 =
  10. 10.40 + 19 =
  11. 11.29 − 9 =
  12. 12.464 − 99 =
  13. 13.15 + 29 =
  14. 14.52 + 9 =
  15. 15.164 + 99 =
  16. 16.48 + 19 =
  17. 17.459 − 99 =
  18. 18.62 − 9 =
  19. 19.20 − 9 =
  20. 20.55 − 19 =
  21. 21.79 + 29 =
  22. 22.36 + 19 =
  23. 23.25 − 9 =
  24. 24.28 + 9 =
  25. 25.519 − 99 =
  26. 26.39 + 29 =
  27. 27.28 + 19 =
  28. 28.109 − 29 =
  29. 29.360 − 99 =
  30. 30.71 − 29 =
  31. 31.590 + 99 =
  32. 32.81 − 29 =
  33. 33.64 + 29 =
  34. 34.39 + 9 =
  35. 35.36 + 9 =
  36. 36.49 + 19 =
  37. 37.15 + 9 =
  38. 38.74 + 19 =
  39. 39.68 + 9 =
  40. 40.29 − 19 =

Answer key

  1. 38
  2. 9
  3. 6
  4. 85
  5. 603
  6. 79
  7. 40
  8. 50
  9. 638
  10. 59
  11. 20
  12. 365
  13. 44
  14. 61
  15. 263
  16. 67
  17. 360
  18. 53
  19. 11
  20. 36
  21. 108
  22. 55
  23. 16
  24. 37
  25. 420
  26. 68
  27. 47
  28. 80
  29. 261
  30. 42
  31. 689
  32. 52
  33. 93
  34. 48
  35. 45
  36. 68
  37. 24
  38. 93
  39. 77
  40. 10

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