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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 500 · 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. 1.66 − 9 =
  2. 2.378 + 99 =
  3. 3.759 + 99 =
  4. 4.74 + 29 =
  5. 5.28 + 19 =
  6. 6.52 + 19 =
  7. 7.52 + 9 =
  8. 8.90 − 19 =
  9. 9.63 − 19 =
  10. 10.33 − 19 =
  11. 11.73 + 29 =
  12. 12.447 − 99 =
  13. 13.706 − 99 =
  14. 14.32 − 29 =
  15. 15.77 − 29 =
  16. 16.100 − 29 =
  17. 17.331 − 99 =
  18. 18.624 − 99 =
  19. 19.71 + 29 =
  20. 20.298 − 99 =
  21. 21.339 − 99 =
  22. 22.70 + 19 =
  23. 23.12 + 9 =
  24. 24.82 − 9 =
  25. 25.68 − 9 =
  26. 26.31 + 9 =
  27. 27.99 − 19 =
  28. 28.50 + 29 =
  29. 29.249 + 99 =
  30. 30.255 + 99 =
  31. 31.49 + 9 =
  32. 32.25 + 29 =
  33. 33.22 + 19 =
  34. 34.67 + 9 =
  35. 35.22 + 9 =
  36. 36.49 − 19 =
  37. 37.17 + 19 =
  38. 38.29 + 19 =
  39. 39.18 + 29 =
  40. 40.53 − 9 =

Answer key

  1. 57
  2. 477
  3. 858
  4. 103
  5. 47
  6. 71
  7. 61
  8. 71
  9. 44
  10. 14
  11. 102
  12. 348
  13. 607
  14. 3
  15. 48
  16. 71
  17. 232
  18. 525
  19. 100
  20. 199
  21. 240
  22. 89
  23. 21
  24. 73
  25. 59
  26. 40
  27. 80
  28. 79
  29. 348
  30. 354
  31. 58
  32. 54
  33. 41
  34. 76
  35. 31
  36. 30
  37. 36
  38. 48
  39. 47
  40. 44

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