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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 813 · 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. 1.69 + 9 =
  2. 2.50 + 29 =
  3. 3.70 − 9 =
  4. 4.71 + 9 =
  5. 5.578 + 99 =
  6. 6.151 − 99 =
  7. 7.34 + 9 =
  8. 8.82 − 9 =
  9. 9.38 + 9 =
  10. 10.28 + 29 =
  11. 11.833 − 99 =
  12. 12.55 − 9 =
  13. 13.40 − 29 =
  14. 14.15 + 29 =
  15. 15.36 − 19 =
  16. 16.27 + 9 =
  17. 17.92 − 19 =
  18. 18.692 − 99 =
  19. 19.44 + 9 =
  20. 20.75 + 9 =
  21. 21.715 + 99 =
  22. 22.74 + 9 =
  23. 23.80 + 29 =
  24. 24.152 + 99 =
  25. 25.377 − 99 =
  26. 26.12 − 9 =
  27. 27.105 − 29 =
  28. 28.71 + 19 =
  29. 29.58 − 29 =
  30. 30.48 − 29 =
  31. 31.57 − 9 =
  32. 32.68 + 19 =
  33. 33.67 − 19 =
  34. 34.23 + 19 =
  35. 35.45 + 19 =
  36. 36.89 − 19 =
  37. 37.60 + 29 =
  38. 38.29 + 9 =
  39. 39.14 + 9 =
  40. 40.98 − 29 =

Answer key

  1. 78
  2. 79
  3. 61
  4. 80
  5. 677
  6. 52
  7. 43
  8. 73
  9. 47
  10. 57
  11. 734
  12. 46
  13. 11
  14. 44
  15. 17
  16. 36
  17. 73
  18. 593
  19. 53
  20. 84
  21. 814
  22. 83
  23. 109
  24. 251
  25. 278
  26. 3
  27. 76
  28. 90
  29. 29
  30. 19
  31. 48
  32. 87
  33. 48
  34. 42
  35. 64
  36. 70
  37. 89
  38. 38
  39. 23
  40. 69

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