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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 396 · 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. 1.183 − 99 =
  2. 2.39 − 9 =
  3. 3.699 + 99 =
  4. 4.76 − 9 =
  5. 5.264 + 99 =
  6. 6.70 + 19 =
  7. 7.45 − 29 =
  8. 8.732 + 99 =
  9. 9.438 − 99 =
  10. 10.22 + 9 =
  11. 11.47 − 29 =
  12. 12.82 − 19 =
  13. 13.695 − 99 =
  14. 14.623 + 99 =
  15. 15.75 + 19 =
  16. 16.74 + 29 =
  17. 17.27 − 19 =
  18. 18.45 − 19 =
  19. 19.37 − 9 =
  20. 20.14 + 9 =
  21. 21.471 − 99 =
  22. 22.93 − 19 =
  23. 23.86 − 9 =
  24. 24.28 − 19 =
  25. 25.40 − 9 =
  26. 26.80 + 29 =
  27. 27.58 + 29 =
  28. 28.17 + 9 =
  29. 29.85 − 19 =
  30. 30.343 − 99 =
  31. 31.246 + 99 =
  32. 32.41 + 19 =
  33. 33.24 + 29 =
  34. 34.68 − 29 =
  35. 35.35 + 9 =
  36. 36.610 + 99 =
  37. 37.55 + 9 =
  38. 38.61 + 19 =
  39. 39.43 − 29 =
  40. 40.54 − 9 =

Answer key

  1. 84
  2. 30
  3. 798
  4. 67
  5. 363
  6. 89
  7. 16
  8. 831
  9. 339
  10. 31
  11. 18
  12. 63
  13. 596
  14. 722
  15. 94
  16. 103
  17. 8
  18. 26
  19. 28
  20. 23
  21. 372
  22. 74
  23. 77
  24. 9
  25. 31
  26. 109
  27. 87
  28. 26
  29. 66
  30. 244
  31. 345
  32. 60
  33. 53
  34. 39
  35. 44
  36. 709
  37. 64
  38. 80
  39. 14
  40. 45

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