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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 340 · 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. 1.81 − 9 =
  2. 2.527 − 99 =
  3. 3.71 − 29 =
  4. 4.67 − 9 =
  5. 5.408 + 99 =
  6. 6.29 + 29 =
  7. 7.603 + 99 =
  8. 8.89 − 9 =
  9. 9.629 − 99 =
  10. 10.733 − 99 =
  11. 11.83 − 19 =
  12. 12.84 − 9 =
  13. 13.652 − 99 =
  14. 14.37 + 29 =
  15. 15.346 + 99 =
  16. 16.73 + 29 =
  17. 17.71 + 9 =
  18. 18.53 − 19 =
  19. 19.56 + 29 =
  20. 20.262 − 99 =
  21. 21.76 − 29 =
  22. 22.74 + 19 =
  23. 23.56 − 29 =
  24. 24.59 − 19 =
  25. 25.67 + 29 =
  26. 26.57 + 29 =
  27. 27.308 + 99 =
  28. 28.28 + 19 =
  29. 29.33 − 29 =
  30. 30.36 − 9 =
  31. 31.32 − 19 =
  32. 32.70 − 29 =
  33. 33.465 + 99 =
  34. 34.14 + 19 =
  35. 35.13 − 9 =
  36. 36.406 + 99 =
  37. 37.61 − 29 =
  38. 38.12 + 9 =
  39. 39.374 − 99 =
  40. 40.99 − 19 =

Answer key

  1. 72
  2. 428
  3. 42
  4. 58
  5. 507
  6. 58
  7. 702
  8. 80
  9. 530
  10. 634
  11. 64
  12. 75
  13. 553
  14. 66
  15. 445
  16. 102
  17. 80
  18. 34
  19. 85
  20. 163
  21. 47
  22. 93
  23. 27
  24. 40
  25. 96
  26. 86
  27. 407
  28. 47
  29. 4
  30. 27
  31. 13
  32. 41
  33. 564
  34. 33
  35. 4
  36. 505
  37. 32
  38. 21
  39. 275
  40. 80

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