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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 229 · 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. 1.86 − 19 =
  2. 2.684 − 99 =
  3. 3.61 − 29 =
  4. 4.94 − 29 =
  5. 5.301 − 99 =
  6. 6.109 − 29 =
  7. 7.42 − 19 =
  8. 8.378 − 99 =
  9. 9.71 + 19 =
  10. 10.34 − 9 =
  11. 11.15 − 9 =
  12. 12.49 + 9 =
  13. 13.55 + 19 =
  14. 14.216 + 99 =
  15. 15.770 + 99 =
  16. 16.30 − 19 =
  17. 17.186 + 99 =
  18. 18.73 + 9 =
  19. 19.80 + 9 =
  20. 20.25 − 19 =
  21. 21.51 − 29 =
  22. 22.71 + 9 =
  23. 23.559 − 99 =
  24. 24.79 + 29 =
  25. 25.67 − 9 =
  26. 26.58 + 9 =
  27. 27.42 + 29 =
  28. 28.74 − 29 =
  29. 29.451 + 99 =
  30. 30.18 − 9 =
  31. 31.42 + 19 =
  32. 32.87 − 19 =
  33. 33.297 + 99 =
  34. 34.39 + 19 =
  35. 35.26 − 19 =
  36. 36.93 − 29 =
  37. 37.88 − 19 =
  38. 38.865 − 99 =
  39. 39.135 + 99 =
  40. 40.71 − 29 =

Answer key

  1. 67
  2. 585
  3. 32
  4. 65
  5. 202
  6. 80
  7. 23
  8. 279
  9. 90
  10. 25
  11. 6
  12. 58
  13. 74
  14. 315
  15. 869
  16. 11
  17. 285
  18. 82
  19. 89
  20. 6
  21. 22
  22. 80
  23. 460
  24. 108
  25. 58
  26. 67
  27. 71
  28. 45
  29. 550
  30. 9
  31. 61
  32. 68
  33. 396
  34. 58
  35. 7
  36. 64
  37. 69
  38. 766
  39. 234
  40. 42

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