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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 814 · 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. 1.486 + 99 =
  2. 2.26 + 19 =
  3. 3.73 − 29 =
  4. 4.58 + 9 =
  5. 5.42 − 9 =
  6. 6.24 − 19 =
  7. 7.69 + 29 =
  8. 8.743 − 99 =
  9. 9.615 + 99 =
  10. 10.496 − 99 =
  11. 11.37 + 9 =
  12. 12.75 − 9 =
  13. 13.13 − 9 =
  14. 14.826 − 99 =
  15. 15.481 − 99 =
  16. 16.58 + 29 =
  17. 17.37 + 29 =
  18. 18.728 − 99 =
  19. 19.30 − 9 =
  20. 20.626 + 99 =
  21. 21.55 + 29 =
  22. 22.52 − 9 =
  23. 23.637 − 99 =
  24. 24.65 + 29 =
  25. 25.453 − 99 =
  26. 26.57 + 19 =
  27. 27.17 + 29 =
  28. 28.224 + 99 =
  29. 29.59 − 9 =
  30. 30.198 − 99 =
  31. 31.79 + 19 =
  32. 32.63 + 19 =
  33. 33.313 − 99 =
  34. 34.12 − 9 =
  35. 35.63 − 19 =
  36. 36.54 + 29 =
  37. 37.17 + 9 =
  38. 38.590 + 99 =
  39. 39.51 + 9 =
  40. 40.21 + 19 =

Answer key

  1. 585
  2. 45
  3. 44
  4. 67
  5. 33
  6. 5
  7. 98
  8. 644
  9. 714
  10. 397
  11. 46
  12. 66
  13. 4
  14. 727
  15. 382
  16. 87
  17. 66
  18. 629
  19. 21
  20. 725
  21. 84
  22. 43
  23. 538
  24. 94
  25. 354
  26. 76
  27. 46
  28. 323
  29. 50
  30. 99
  31. 98
  32. 82
  33. 214
  34. 3
  35. 44
  36. 83
  37. 26
  38. 689
  39. 60
  40. 40

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