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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 798 · 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. 1.417 + 99 =
  2. 2.326 + 99 =
  3. 3.62 − 9 =
  4. 4.56 + 19 =
  5. 5.52 − 9 =
  6. 6.62 + 19 =
  7. 7.28 − 19 =
  8. 8.82 − 19 =
  9. 9.62 + 29 =
  10. 10.415 − 99 =
  11. 11.215 − 99 =
  12. 12.102 − 29 =
  13. 13.68 − 29 =
  14. 14.78 + 19 =
  15. 15.660 + 99 =
  16. 16.523 − 99 =
  17. 17.108 − 29 =
  18. 18.16 + 19 =
  19. 19.28 − 9 =
  20. 20.93 − 29 =
  21. 21.17 − 9 =
  22. 22.54 + 9 =
  23. 23.15 − 9 =
  24. 24.315 − 99 =
  25. 25.58 + 9 =
  26. 26.25 + 19 =
  27. 27.657 + 99 =
  28. 28.427 − 99 =
  29. 29.278 + 99 =
  30. 30.32 − 9 =
  31. 31.30 − 9 =
  32. 32.79 + 19 =
  33. 33.49 − 9 =
  34. 34.65 + 19 =
  35. 35.27 − 9 =
  36. 36.14 − 9 =
  37. 37.764 − 99 =
  38. 38.23 + 19 =
  39. 39.16 − 9 =
  40. 40.40 − 29 =

Answer key

  1. 516
  2. 425
  3. 53
  4. 75
  5. 43
  6. 81
  7. 9
  8. 63
  9. 91
  10. 316
  11. 116
  12. 73
  13. 39
  14. 97
  15. 759
  16. 424
  17. 79
  18. 35
  19. 19
  20. 64
  21. 8
  22. 63
  23. 6
  24. 216
  25. 67
  26. 44
  27. 756
  28. 328
  29. 377
  30. 23
  31. 21
  32. 98
  33. 40
  34. 84
  35. 18
  36. 5
  37. 665
  38. 42
  39. 7
  40. 11

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