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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 358 · 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. 1.31 − 9 =
  2. 2.465 + 99 =
  3. 3.105 − 29 =
  4. 4.67 − 19 =
  5. 5.189 − 99 =
  6. 6.71 − 19 =
  7. 7.25 + 19 =
  8. 8.262 + 99 =
  9. 9.54 + 9 =
  10. 10.71 + 29 =
  11. 11.40 + 9 =
  12. 12.746 + 99 =
  13. 13.472 − 99 =
  14. 14.96 − 29 =
  15. 15.68 − 9 =
  16. 16.72 + 19 =
  17. 17.35 − 19 =
  18. 18.672 − 99 =
  19. 19.610 + 99 =
  20. 20.25 − 19 =
  21. 21.106 − 29 =
  22. 22.66 + 9 =
  23. 23.41 + 29 =
  24. 24.353 + 99 =
  25. 25.28 + 19 =
  26. 26.494 + 99 =
  27. 27.56 + 29 =
  28. 28.42 + 19 =
  29. 29.567 + 99 =
  30. 30.30 − 19 =
  31. 31.43 + 9 =
  32. 32.71 + 19 =
  33. 33.34 + 19 =
  34. 34.51 + 29 =
  35. 35.60 + 9 =
  36. 36.64 + 29 =
  37. 37.21 + 9 =
  38. 38.76 − 19 =
  39. 39.376 − 99 =
  40. 40.53 + 9 =

Answer key

  1. 22
  2. 564
  3. 76
  4. 48
  5. 90
  6. 52
  7. 44
  8. 361
  9. 63
  10. 100
  11. 49
  12. 845
  13. 373
  14. 67
  15. 59
  16. 91
  17. 16
  18. 573
  19. 709
  20. 6
  21. 77
  22. 75
  23. 70
  24. 452
  25. 47
  26. 593
  27. 85
  28. 61
  29. 666
  30. 11
  31. 52
  32. 90
  33. 53
  34. 80
  35. 69
  36. 93
  37. 30
  38. 57
  39. 277
  40. 62

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