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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 776 · 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. 1.42 + 29 =
  2. 2.60 + 9 =
  3. 3.42 − 9 =
  4. 4.24 − 9 =
  5. 5.48 − 9 =
  6. 6.43 − 29 =
  7. 7.444 − 99 =
  8. 8.717 + 99 =
  9. 9.62 + 19 =
  10. 10.70 − 19 =
  11. 11.60 + 29 =
  12. 12.64 − 9 =
  13. 13.44 + 19 =
  14. 14.29 + 29 =
  15. 15.63 + 9 =
  16. 16.67 + 19 =
  17. 17.97 − 29 =
  18. 18.302 − 99 =
  19. 19.387 + 99 =
  20. 20.26 + 9 =
  21. 21.585 − 99 =
  22. 22.286 + 99 =
  23. 23.39 + 9 =
  24. 24.798 + 99 =
  25. 25.318 − 99 =
  26. 26.73 + 29 =
  27. 27.79 + 19 =
  28. 28.791 − 99 =
  29. 29.24 + 19 =
  30. 30.65 − 29 =
  31. 31.26 + 19 =
  32. 32.98 − 29 =
  33. 33.204 + 99 =
  34. 34.577 − 99 =
  35. 35.71 − 9 =
  36. 36.765 + 99 =
  37. 37.37 + 29 =
  38. 38.131 + 99 =
  39. 39.57 + 29 =
  40. 40.21 + 29 =

Answer key

  1. 71
  2. 69
  3. 33
  4. 15
  5. 39
  6. 14
  7. 345
  8. 816
  9. 81
  10. 51
  11. 89
  12. 55
  13. 63
  14. 58
  15. 72
  16. 86
  17. 68
  18. 203
  19. 486
  20. 35
  21. 486
  22. 385
  23. 48
  24. 897
  25. 219
  26. 102
  27. 98
  28. 692
  29. 43
  30. 36
  31. 45
  32. 69
  33. 303
  34. 478
  35. 62
  36. 864
  37. 66
  38. 230
  39. 86
  40. 50

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