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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 973 · 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 − 19 =
  2. 2.712 − 99 =
  3. 3.65 + 9 =
  4. 4.96 − 19 =
  5. 5.77 − 29 =
  6. 6.83 − 29 =
  7. 7.77 + 29 =
  8. 8.63 + 19 =
  9. 9.26 − 19 =
  10. 10.61 + 19 =
  11. 11.377 − 99 =
  12. 12.20 + 29 =
  13. 13.29 + 29 =
  14. 14.59 − 29 =
  15. 15.754 + 99 =
  16. 16.42 + 9 =
  17. 17.36 + 19 =
  18. 18.49 + 9 =
  19. 19.237 − 99 =
  20. 20.71 − 9 =
  21. 21.74 + 19 =
  22. 22.29 − 19 =
  23. 23.343 − 99 =
  24. 24.57 − 9 =
  25. 25.73 − 19 =
  26. 26.398 − 99 =
  27. 27.58 − 9 =
  28. 28.536 − 99 =
  29. 29.46 − 9 =
  30. 30.704 + 99 =
  31. 31.887 − 99 =
  32. 32.39 + 29 =
  33. 33.38 + 29 =
  34. 34.44 + 29 =
  35. 35.54 − 19 =
  36. 36.37 + 9 =
  37. 37.83 − 9 =
  38. 38.52 − 19 =
  39. 39.31 + 9 =
  40. 40.93 − 19 =

Answer key

  1. 12
  2. 613
  3. 74
  4. 77
  5. 48
  6. 54
  7. 106
  8. 82
  9. 7
  10. 80
  11. 278
  12. 49
  13. 58
  14. 30
  15. 853
  16. 51
  17. 55
  18. 58
  19. 138
  20. 62
  21. 93
  22. 10
  23. 244
  24. 48
  25. 54
  26. 299
  27. 49
  28. 437
  29. 37
  30. 803
  31. 788
  32. 68
  33. 67
  34. 73
  35. 35
  36. 46
  37. 74
  38. 33
  39. 40
  40. 74

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