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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 62 · 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. 1.85 − 9 =
  2. 2.214 − 99 =
  3. 3.278 + 99 =
  4. 4.508 − 99 =
  5. 5.78 + 29 =
  6. 6.67 + 19 =
  7. 7.62 − 9 =
  8. 8.29 + 19 =
  9. 9.41 − 29 =
  10. 10.36 + 9 =
  11. 11.12 + 9 =
  12. 12.37 + 29 =
  13. 13.58 + 9 =
  14. 14.86 − 29 =
  15. 15.80 − 9 =
  16. 16.27 − 9 =
  17. 17.35 − 19 =
  18. 18.28 + 19 =
  19. 19.64 + 19 =
  20. 20.38 − 9 =
  21. 21.396 − 99 =
  22. 22.19 + 29 =
  23. 23.46 + 29 =
  24. 24.17 + 19 =
  25. 25.17 + 29 =
  26. 26.153 − 99 =
  27. 27.80 + 29 =
  28. 28.392 + 99 =
  29. 29.66 − 19 =
  30. 30.82 − 9 =
  31. 31.37 − 29 =
  32. 32.73 + 19 =
  33. 33.31 + 9 =
  34. 34.58 + 29 =
  35. 35.53 + 29 =
  36. 36.744 − 99 =
  37. 37.25 + 19 =
  38. 38.647 − 99 =
  39. 39.154 − 99 =
  40. 40.25 − 9 =

Answer key

  1. 76
  2. 115
  3. 377
  4. 409
  5. 107
  6. 86
  7. 53
  8. 48
  9. 12
  10. 45
  11. 21
  12. 66
  13. 67
  14. 57
  15. 71
  16. 18
  17. 16
  18. 47
  19. 83
  20. 29
  21. 297
  22. 48
  23. 75
  24. 36
  25. 46
  26. 54
  27. 109
  28. 491
  29. 47
  30. 73
  31. 8
  32. 92
  33. 40
  34. 87
  35. 82
  36. 645
  37. 44
  38. 548
  39. 55
  40. 16

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