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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 420 · 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. 1.72 − 29 =
  2. 2.25 + 19 =
  3. 3.26 + 29 =
  4. 4.63 + 19 =
  5. 5.32 + 9 =
  6. 6.19 + 9 =
  7. 7.66 − 19 =
  8. 8.42 − 29 =
  9. 9.866 − 99 =
  10. 10.24 + 9 =
  11. 11.22 + 9 =
  12. 12.72 + 9 =
  13. 13.80 − 9 =
  14. 14.47 + 19 =
  15. 15.157 − 99 =
  16. 16.18 − 9 =
  17. 17.62 − 9 =
  18. 18.76 + 9 =
  19. 19.27 − 9 =
  20. 20.68 + 9 =
  21. 21.55 − 19 =
  22. 22.59 + 9 =
  23. 23.49 + 9 =
  24. 24.713 − 99 =
  25. 25.81 − 19 =
  26. 26.23 + 29 =
  27. 27.530 − 99 =
  28. 28.96 − 29 =
  29. 29.277 + 99 =
  30. 30.19 − 9 =
  31. 31.94 − 19 =
  32. 32.21 + 9 =
  33. 33.42 + 29 =
  34. 34.570 − 99 =
  35. 35.323 − 99 =
  36. 36.55 + 29 =
  37. 37.196 − 99 =
  38. 38.890 − 99 =
  39. 39.283 − 99 =
  40. 40.54 + 19 =

Answer key

  1. 43
  2. 44
  3. 55
  4. 82
  5. 41
  6. 28
  7. 47
  8. 13
  9. 767
  10. 33
  11. 31
  12. 81
  13. 71
  14. 66
  15. 58
  16. 9
  17. 53
  18. 85
  19. 18
  20. 77
  21. 36
  22. 68
  23. 58
  24. 614
  25. 62
  26. 52
  27. 431
  28. 67
  29. 376
  30. 10
  31. 75
  32. 30
  33. 71
  34. 471
  35. 224
  36. 84
  37. 97
  38. 791
  39. 184
  40. 73

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