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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 743 · 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. 1.698 − 99 =
  2. 2.156 − 99 =
  3. 3.95 − 19 =
  4. 4.94 − 19 =
  5. 5.40 − 29 =
  6. 6.15 + 29 =
  7. 7.24 + 19 =
  8. 8.49 + 19 =
  9. 9.290 + 99 =
  10. 10.32 + 19 =
  11. 11.89 − 19 =
  12. 12.473 − 99 =
  13. 13.410 − 99 =
  14. 14.23 + 9 =
  15. 15.37 − 9 =
  16. 16.37 − 19 =
  17. 17.304 + 99 =
  18. 18.50 − 29 =
  19. 19.76 + 9 =
  20. 20.22 − 9 =
  21. 21.88 − 9 =
  22. 22.88 − 19 =
  23. 23.13 + 9 =
  24. 24.651 + 99 =
  25. 25.65 − 9 =
  26. 26.48 + 19 =
  27. 27.68 − 29 =
  28. 28.22 − 19 =
  29. 29.518 + 99 =
  30. 30.44 + 9 =
  31. 31.42 + 9 =
  32. 32.28 + 29 =
  33. 33.33 + 19 =
  34. 34.52 + 29 =
  35. 35.20 + 9 =
  36. 36.61 − 29 =
  37. 37.34 + 29 =
  38. 38.39 − 29 =
  39. 39.704 + 99 =
  40. 40.72 + 19 =

Answer key

  1. 599
  2. 57
  3. 76
  4. 75
  5. 11
  6. 44
  7. 43
  8. 68
  9. 389
  10. 51
  11. 70
  12. 374
  13. 311
  14. 32
  15. 28
  16. 18
  17. 403
  18. 21
  19. 85
  20. 13
  21. 79
  22. 69
  23. 22
  24. 750
  25. 56
  26. 67
  27. 39
  28. 3
  29. 617
  30. 53
  31. 51
  32. 57
  33. 52
  34. 81
  35. 29
  36. 32
  37. 63
  38. 10
  39. 803
  40. 91

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