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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 12 · 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. 1.71 − 9 =
  2. 2.651 − 99 =
  3. 3.440 + 99 =
  4. 4.13 + 19 =
  5. 5.107 − 29 =
  6. 6.85 − 19 =
  7. 7.26 + 9 =
  8. 8.22 + 29 =
  9. 9.45 − 29 =
  10. 10.549 − 99 =
  11. 11.71 − 29 =
  12. 12.90 − 19 =
  13. 13.382 − 99 =
  14. 14.419 − 99 =
  15. 15.96 − 19 =
  16. 16.83 − 9 =
  17. 17.46 + 19 =
  18. 18.239 + 99 =
  19. 19.22 − 19 =
  20. 20.13 − 9 =
  21. 21.184 + 99 =
  22. 22.53 − 19 =
  23. 23.27 − 9 =
  24. 24.29 + 19 =
  25. 25.106 − 29 =
  26. 26.51 + 29 =
  27. 27.72 − 19 =
  28. 28.100 − 29 =
  29. 29.63 − 19 =
  30. 30.33 − 9 =
  31. 31.30 − 9 =
  32. 32.28 + 9 =
  33. 33.276 − 99 =
  34. 34.19 + 29 =
  35. 35.558 − 99 =
  36. 36.15 + 9 =
  37. 37.58 + 19 =
  38. 38.33 + 29 =
  39. 39.43 + 29 =
  40. 40.117 + 99 =

Answer key

  1. 62
  2. 552
  3. 539
  4. 32
  5. 78
  6. 66
  7. 35
  8. 51
  9. 16
  10. 450
  11. 42
  12. 71
  13. 283
  14. 320
  15. 77
  16. 74
  17. 65
  18. 338
  19. 3
  20. 4
  21. 283
  22. 34
  23. 18
  24. 48
  25. 77
  26. 80
  27. 53
  28. 71
  29. 44
  30. 24
  31. 21
  32. 37
  33. 177
  34. 48
  35. 459
  36. 24
  37. 77
  38. 62
  39. 72
  40. 216

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