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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 560 · 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. 1.66 − 29 =
  2. 2.57 − 9 =
  3. 3.63 + 29 =
  4. 4.79 + 19 =
  5. 5.541 − 99 =
  6. 6.694 − 99 =
  7. 7.85 − 9 =
  8. 8.498 − 99 =
  9. 9.33 − 9 =
  10. 10.195 + 99 =
  11. 11.13 + 9 =
  12. 12.32 + 9 =
  13. 13.29 + 9 =
  14. 14.30 + 19 =
  15. 15.65 + 19 =
  16. 16.30 + 9 =
  17. 17.49 + 29 =
  18. 18.59 − 19 =
  19. 19.697 + 99 =
  20. 20.59 − 29 =
  21. 21.64 − 19 =
  22. 22.285 − 99 =
  23. 23.631 + 99 =
  24. 24.96 − 29 =
  25. 25.19 − 9 =
  26. 26.46 − 19 =
  27. 27.48 − 29 =
  28. 28.32 − 9 =
  29. 29.40 − 19 =
  30. 30.73 + 19 =
  31. 31.297 − 99 =
  32. 32.57 + 19 =
  33. 33.584 − 99 =
  34. 34.71 + 19 =
  35. 35.723 + 99 =
  36. 36.80 + 9 =
  37. 37.44 + 9 =
  38. 38.63 − 29 =
  39. 39.54 − 9 =
  40. 40.92 − 29 =

Answer key

  1. 37
  2. 48
  3. 92
  4. 98
  5. 442
  6. 595
  7. 76
  8. 399
  9. 24
  10. 294
  11. 22
  12. 41
  13. 38
  14. 49
  15. 84
  16. 39
  17. 78
  18. 40
  19. 796
  20. 30
  21. 45
  22. 186
  23. 730
  24. 67
  25. 10
  26. 27
  27. 19
  28. 23
  29. 21
  30. 92
  31. 198
  32. 76
  33. 485
  34. 90
  35. 822
  36. 89
  37. 53
  38. 34
  39. 45
  40. 63

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