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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 90 · 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. 1.690 + 99 =
  2. 2.77 + 19 =
  3. 3.216 + 99 =
  4. 4.194 − 99 =
  5. 5.751 − 99 =
  6. 6.26 + 9 =
  7. 7.74 − 29 =
  8. 8.38 − 19 =
  9. 9.262 − 99 =
  10. 10.53 + 19 =
  11. 11.15 − 9 =
  12. 12.61 − 9 =
  13. 13.52 + 29 =
  14. 14.25 − 19 =
  15. 15.76 + 29 =
  16. 16.51 − 9 =
  17. 17.87 − 9 =
  18. 18.57 + 19 =
  19. 19.75 − 29 =
  20. 20.12 − 9 =
  21. 21.15 + 9 =
  22. 22.14 − 9 =
  23. 23.29 − 19 =
  24. 24.109 − 29 =
  25. 25.46 − 19 =
  26. 26.91 − 29 =
  27. 27.495 + 99 =
  28. 28.78 − 9 =
  29. 29.18 + 19 =
  30. 30.38 + 19 =
  31. 31.59 − 9 =
  32. 32.61 + 29 =
  33. 33.62 + 9 =
  34. 34.35 − 29 =
  35. 35.47 − 19 =
  36. 36.73 + 29 =
  37. 37.19 − 9 =
  38. 38.34 − 19 =
  39. 39.54 − 29 =
  40. 40.53 + 9 =

Answer key

  1. 789
  2. 96
  3. 315
  4. 95
  5. 652
  6. 35
  7. 45
  8. 19
  9. 163
  10. 72
  11. 6
  12. 52
  13. 81
  14. 6
  15. 105
  16. 42
  17. 78
  18. 76
  19. 46
  20. 3
  21. 24
  22. 5
  23. 10
  24. 80
  25. 27
  26. 62
  27. 594
  28. 69
  29. 37
  30. 57
  31. 50
  32. 90
  33. 71
  34. 6
  35. 28
  36. 102
  37. 10
  38. 15
  39. 25
  40. 62

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