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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 864 · 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. 1.19 − 9 =
  2. 2.61 + 9 =
  3. 3.25 + 19 =
  4. 4.830 − 99 =
  5. 5.43 + 9 =
  6. 6.302 − 99 =
  7. 7.74 − 29 =
  8. 8.33 + 9 =
  9. 9.51 + 19 =
  10. 10.359 + 99 =
  11. 11.44 − 9 =
  12. 12.466 + 99 =
  13. 13.92 − 29 =
  14. 14.200 + 99 =
  15. 15.288 + 99 =
  16. 16.65 + 9 =
  17. 17.52 + 19 =
  18. 18.44 + 9 =
  19. 19.684 + 99 =
  20. 20.15 − 9 =
  21. 21.596 + 99 =
  22. 22.54 + 19 =
  23. 23.52 + 29 =
  24. 24.13 + 29 =
  25. 25.38 + 29 =
  26. 26.594 + 99 =
  27. 27.43 + 29 =
  28. 28.34 − 9 =
  29. 29.743 + 99 =
  30. 30.65 − 19 =
  31. 31.76 + 19 =
  32. 32.25 + 9 =
  33. 33.71 + 9 =
  34. 34.64 − 19 =
  35. 35.51 − 29 =
  36. 36.89 − 9 =
  37. 37.755 − 99 =
  38. 38.36 + 29 =
  39. 39.53 − 29 =
  40. 40.21 + 19 =

Answer key

  1. 10
  2. 70
  3. 44
  4. 731
  5. 52
  6. 203
  7. 45
  8. 42
  9. 70
  10. 458
  11. 35
  12. 565
  13. 63
  14. 299
  15. 387
  16. 74
  17. 71
  18. 53
  19. 783
  20. 6
  21. 695
  22. 73
  23. 81
  24. 42
  25. 67
  26. 693
  27. 72
  28. 25
  29. 842
  30. 46
  31. 95
  32. 34
  33. 80
  34. 45
  35. 22
  36. 80
  37. 656
  38. 65
  39. 24
  40. 40

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