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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 791 · 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. 1.37 + 29 =
  2. 2.24 + 19 =
  3. 3.13 + 29 =
  4. 4.42 − 9 =
  5. 5.21 + 9 =
  6. 6.52 − 19 =
  7. 7.71 + 29 =
  8. 8.41 + 9 =
  9. 9.212 − 99 =
  10. 10.38 + 29 =
  11. 11.70 − 29 =
  12. 12.44 − 29 =
  13. 13.72 + 19 =
  14. 14.28 − 9 =
  15. 15.86 − 19 =
  16. 16.84 − 9 =
  17. 17.45 − 29 =
  18. 18.269 + 99 =
  19. 19.55 − 9 =
  20. 20.70 + 19 =
  21. 21.506 + 99 =
  22. 22.47 + 9 =
  23. 23.21 − 9 =
  24. 24.19 − 9 =
  25. 25.355 − 99 =
  26. 26.66 − 29 =
  27. 27.25 + 19 =
  28. 28.62 + 9 =
  29. 29.709 + 99 =
  30. 30.29 + 29 =
  31. 31.27 − 9 =
  32. 32.40 − 9 =
  33. 33.381 + 99 =
  34. 34.103 − 29 =
  35. 35.62 − 9 =
  36. 36.64 + 9 =
  37. 37.458 + 99 =
  38. 38.66 + 29 =
  39. 39.74 + 19 =
  40. 40.741 − 99 =

Answer key

  1. 66
  2. 43
  3. 42
  4. 33
  5. 30
  6. 33
  7. 100
  8. 50
  9. 113
  10. 67
  11. 41
  12. 15
  13. 91
  14. 19
  15. 67
  16. 75
  17. 16
  18. 368
  19. 46
  20. 89
  21. 605
  22. 56
  23. 12
  24. 10
  25. 256
  26. 37
  27. 44
  28. 71
  29. 808
  30. 58
  31. 18
  32. 31
  33. 480
  34. 74
  35. 53
  36. 73
  37. 557
  38. 95
  39. 93
  40. 642

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