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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 636 · 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. 1.12 + 19 =
  2. 2.46 + 19 =
  3. 3.482 + 99 =
  4. 4.263 + 99 =
  5. 5.56 − 19 =
  6. 6.78 + 29 =
  7. 7.50 + 9 =
  8. 8.632 + 99 =
  9. 9.74 + 19 =
  10. 10.65 + 19 =
  11. 11.45 − 19 =
  12. 12.70 + 19 =
  13. 13.36 + 19 =
  14. 14.31 − 19 =
  15. 15.13 + 9 =
  16. 16.28 + 29 =
  17. 17.35 + 19 =
  18. 18.625 − 99 =
  19. 19.551 − 99 =
  20. 20.46 + 29 =
  21. 21.47 + 9 =
  22. 22.17 + 9 =
  23. 23.40 + 19 =
  24. 24.770 − 99 =
  25. 25.45 + 29 =
  26. 26.38 + 9 =
  27. 27.376 − 99 =
  28. 28.48 − 9 =
  29. 29.328 − 99 =
  30. 30.71 + 9 =
  31. 31.183 − 99 =
  32. 32.91 − 29 =
  33. 33.37 − 29 =
  34. 34.17 + 19 =
  35. 35.78 + 9 =
  36. 36.24 + 29 =
  37. 37.69 + 9 =
  38. 38.751 − 99 =
  39. 39.65 + 9 =
  40. 40.51 − 9 =

Answer key

  1. 31
  2. 65
  3. 581
  4. 362
  5. 37
  6. 107
  7. 59
  8. 731
  9. 93
  10. 84
  11. 26
  12. 89
  13. 55
  14. 12
  15. 22
  16. 57
  17. 54
  18. 526
  19. 452
  20. 75
  21. 56
  22. 26
  23. 59
  24. 671
  25. 74
  26. 47
  27. 277
  28. 39
  29. 229
  30. 80
  31. 84
  32. 62
  33. 8
  34. 36
  35. 87
  36. 53
  37. 78
  38. 652
  39. 74
  40. 42

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