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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 100 · 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. 1.51 + 29 =
  2. 2.792 + 99 =
  3. 3.419 + 99 =
  4. 4.76 + 9 =
  5. 5.31 + 19 =
  6. 6.48 + 29 =
  7. 7.56 + 9 =
  8. 8.50 + 9 =
  9. 9.59 + 29 =
  10. 10.14 + 9 =
  11. 11.59 − 29 =
  12. 12.46 + 9 =
  13. 13.29 + 19 =
  14. 14.39 − 19 =
  15. 15.70 − 9 =
  16. 16.747 − 99 =
  17. 17.620 + 99 =
  18. 18.19 + 9 =
  19. 19.61 + 29 =
  20. 20.93 − 29 =
  21. 21.583 + 99 =
  22. 22.195 − 99 =
  23. 23.38 − 19 =
  24. 24.66 + 9 =
  25. 25.72 − 19 =
  26. 26.13 + 9 =
  27. 27.39 + 19 =
  28. 28.729 + 99 =
  29. 29.102 − 29 =
  30. 30.42 + 9 =
  31. 31.78 − 19 =
  32. 32.238 − 99 =
  33. 33.16 − 9 =
  34. 34.483 + 99 =
  35. 35.82 − 19 =
  36. 36.64 + 29 =
  37. 37.59 − 9 =
  38. 38.34 − 19 =
  39. 39.19 + 19 =
  40. 40.55 + 29 =

Answer key

  1. 80
  2. 891
  3. 518
  4. 85
  5. 50
  6. 77
  7. 65
  8. 59
  9. 88
  10. 23
  11. 30
  12. 55
  13. 48
  14. 20
  15. 61
  16. 648
  17. 719
  18. 28
  19. 90
  20. 64
  21. 682
  22. 96
  23. 19
  24. 75
  25. 53
  26. 22
  27. 58
  28. 828
  29. 73
  30. 51
  31. 59
  32. 139
  33. 7
  34. 582
  35. 63
  36. 93
  37. 50
  38. 15
  39. 38
  40. 84

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