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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 494 · 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. 1.62 − 9 =
  2. 2.73 + 19 =
  3. 3.69 + 29 =
  4. 4.496 − 99 =
  5. 5.295 + 99 =
  6. 6.211 + 99 =
  7. 7.76 − 19 =
  8. 8.18 + 19 =
  9. 9.24 + 9 =
  10. 10.39 − 19 =
  11. 11.29 − 9 =
  12. 12.273 − 99 =
  13. 13.35 + 9 =
  14. 14.57 + 29 =
  15. 15.39 + 19 =
  16. 16.40 − 19 =
  17. 17.21 − 9 =
  18. 18.62 + 9 =
  19. 19.70 + 9 =
  20. 20.46 + 29 =
  21. 21.535 + 99 =
  22. 22.108 − 29 =
  23. 23.201 − 99 =
  24. 24.624 + 99 =
  25. 25.65 + 29 =
  26. 26.202 − 99 =
  27. 27.82 − 9 =
  28. 28.304 + 99 =
  29. 29.41 − 19 =
  30. 30.201 + 99 =
  31. 31.21 + 9 =
  32. 32.59 − 29 =
  33. 33.77 − 9 =
  34. 34.323 − 99 =
  35. 35.798 + 99 =
  36. 36.40 + 19 =
  37. 37.785 − 99 =
  38. 38.443 + 99 =
  39. 39.79 + 9 =
  40. 40.613 + 99 =

Answer key

  1. 53
  2. 92
  3. 98
  4. 397
  5. 394
  6. 310
  7. 57
  8. 37
  9. 33
  10. 20
  11. 20
  12. 174
  13. 44
  14. 86
  15. 58
  16. 21
  17. 12
  18. 71
  19. 79
  20. 75
  21. 634
  22. 79
  23. 102
  24. 723
  25. 94
  26. 103
  27. 73
  28. 403
  29. 22
  30. 300
  31. 30
  32. 30
  33. 68
  34. 224
  35. 897
  36. 59
  37. 686
  38. 542
  39. 88
  40. 712

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