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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 904 · 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. 1.30 + 19 =
  2. 2.96 − 29 =
  3. 3.12 + 9 =
  4. 4.88 − 9 =
  5. 5.533 + 99 =
  6. 6.52 − 19 =
  7. 7.95 − 29 =
  8. 8.38 − 29 =
  9. 9.373 + 99 =
  10. 10.70 + 9 =
  11. 11.215 + 99 =
  12. 12.37 + 29 =
  13. 13.72 − 19 =
  14. 14.45 − 29 =
  15. 15.74 + 29 =
  16. 16.28 + 19 =
  17. 17.89 − 29 =
  18. 18.67 − 9 =
  19. 19.192 − 99 =
  20. 20.58 + 19 =
  21. 21.27 + 29 =
  22. 22.14 + 9 =
  23. 23.18 + 29 =
  24. 24.61 − 29 =
  25. 25.24 − 19 =
  26. 26.619 − 99 =
  27. 27.46 − 9 =
  28. 28.42 + 29 =
  29. 29.23 + 9 =
  30. 30.160 + 99 =
  31. 31.469 − 99 =
  32. 32.97 − 19 =
  33. 33.61 + 29 =
  34. 34.81 − 19 =
  35. 35.77 − 19 =
  36. 36.799 + 99 =
  37. 37.39 − 19 =
  38. 38.71 + 9 =
  39. 39.585 + 99 =
  40. 40.679 + 99 =

Answer key

  1. 49
  2. 67
  3. 21
  4. 79
  5. 632
  6. 33
  7. 66
  8. 9
  9. 472
  10. 79
  11. 314
  12. 66
  13. 53
  14. 16
  15. 103
  16. 47
  17. 60
  18. 58
  19. 93
  20. 77
  21. 56
  22. 23
  23. 47
  24. 32
  25. 5
  26. 520
  27. 37
  28. 71
  29. 32
  30. 259
  31. 370
  32. 78
  33. 90
  34. 62
  35. 58
  36. 898
  37. 20
  38. 80
  39. 684
  40. 778

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