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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 422 · 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. 1.74 − 29 =
  2. 2.84 − 29 =
  3. 3.68 + 9 =
  4. 4.15 + 9 =
  5. 5.154 − 99 =
  6. 6.29 + 9 =
  7. 7.42 − 29 =
  8. 8.99 − 29 =
  9. 9.36 − 19 =
  10. 10.14 + 19 =
  11. 11.65 + 29 =
  12. 12.40 + 29 =
  13. 13.50 + 9 =
  14. 14.62 − 9 =
  15. 15.62 − 19 =
  16. 16.180 − 99 =
  17. 17.30 + 9 =
  18. 18.49 − 9 =
  19. 19.65 + 9 =
  20. 20.690 − 99 =
  21. 21.492 − 99 =
  22. 22.57 + 29 =
  23. 23.340 − 99 =
  24. 24.44 + 9 =
  25. 25.195 + 99 =
  26. 26.24 − 19 =
  27. 27.788 + 99 =
  28. 28.52 + 19 =
  29. 29.60 + 29 =
  30. 30.43 − 29 =
  31. 31.52 − 29 =
  32. 32.79 + 29 =
  33. 33.544 + 99 =
  34. 34.37 + 9 =
  35. 35.45 − 29 =
  36. 36.69 + 29 =
  37. 37.28 + 9 =
  38. 38.75 + 9 =
  39. 39.329 − 99 =
  40. 40.282 + 99 =

Answer key

  1. 45
  2. 55
  3. 77
  4. 24
  5. 55
  6. 38
  7. 13
  8. 70
  9. 17
  10. 33
  11. 94
  12. 69
  13. 59
  14. 53
  15. 43
  16. 81
  17. 39
  18. 40
  19. 74
  20. 591
  21. 393
  22. 86
  23. 241
  24. 53
  25. 294
  26. 5
  27. 887
  28. 71
  29. 89
  30. 14
  31. 23
  32. 108
  33. 643
  34. 46
  35. 16
  36. 98
  37. 37
  38. 84
  39. 230
  40. 381

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