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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 673 · 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. 1.786 − 99 =
  2. 2.47 − 9 =
  3. 3.70 − 29 =
  4. 4.480 − 99 =
  5. 5.14 − 9 =
  6. 6.13 + 29 =
  7. 7.31 − 19 =
  8. 8.97 − 29 =
  9. 9.59 + 29 =
  10. 10.71 − 19 =
  11. 11.53 − 9 =
  12. 12.60 + 9 =
  13. 13.297 + 99 =
  14. 14.27 + 9 =
  15. 15.30 + 29 =
  16. 16.65 − 9 =
  17. 17.240 + 99 =
  18. 18.60 − 19 =
  19. 19.496 + 99 =
  20. 20.70 + 9 =
  21. 21.33 + 29 =
  22. 22.31 + 29 =
  23. 23.17 + 9 =
  24. 24.52 + 29 =
  25. 25.37 + 9 =
  26. 26.640 + 99 =
  27. 27.55 + 9 =
  28. 28.29 − 19 =
  29. 29.61 − 9 =
  30. 30.69 + 19 =
  31. 31.49 + 29 =
  32. 32.50 + 19 =
  33. 33.253 − 99 =
  34. 34.24 + 9 =
  35. 35.145 + 99 =
  36. 36.219 − 99 =
  37. 37.836 − 99 =
  38. 38.42 + 9 =
  39. 39.23 − 9 =
  40. 40.47 + 19 =

Answer key

  1. 687
  2. 38
  3. 41
  4. 381
  5. 5
  6. 42
  7. 12
  8. 68
  9. 88
  10. 52
  11. 44
  12. 69
  13. 396
  14. 36
  15. 59
  16. 56
  17. 339
  18. 41
  19. 595
  20. 79
  21. 62
  22. 60
  23. 26
  24. 81
  25. 46
  26. 739
  27. 64
  28. 10
  29. 52
  30. 88
  31. 78
  32. 69
  33. 154
  34. 33
  35. 244
  36. 120
  37. 737
  38. 51
  39. 14
  40. 66

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