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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 790 · 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. 1.32 + 29 =
  2. 2.66 + 9 =
  3. 3.56 − 19 =
  4. 4.101 − 29 =
  5. 5.630 − 99 =
  6. 6.30 − 19 =
  7. 7.358 + 99 =
  8. 8.25 − 19 =
  9. 9.258 + 99 =
  10. 10.27 + 29 =
  11. 11.22 + 9 =
  12. 12.525 + 99 =
  13. 13.35 − 29 =
  14. 14.33 + 29 =
  15. 15.830 − 99 =
  16. 16.71 + 29 =
  17. 17.60 − 29 =
  18. 18.505 + 99 =
  19. 19.69 + 19 =
  20. 20.235 − 99 =
  21. 21.58 − 19 =
  22. 22.596 + 99 =
  23. 23.844 − 99 =
  24. 24.546 − 99 =
  25. 25.112 + 99 =
  26. 26.98 − 19 =
  27. 27.77 + 9 =
  28. 28.754 − 99 =
  29. 29.75 − 9 =
  30. 30.70 + 9 =
  31. 31.26 + 29 =
  32. 32.32 − 29 =
  33. 33.46 + 19 =
  34. 34.79 + 29 =
  35. 35.31 + 9 =
  36. 36.44 + 19 =
  37. 37.78 + 9 =
  38. 38.356 + 99 =
  39. 39.107 − 29 =
  40. 40.893 − 99 =

Answer key

  1. 61
  2. 75
  3. 37
  4. 72
  5. 531
  6. 11
  7. 457
  8. 6
  9. 357
  10. 56
  11. 31
  12. 624
  13. 6
  14. 62
  15. 731
  16. 100
  17. 31
  18. 604
  19. 88
  20. 136
  21. 39
  22. 695
  23. 745
  24. 447
  25. 211
  26. 79
  27. 86
  28. 655
  29. 66
  30. 79
  31. 55
  32. 3
  33. 65
  34. 108
  35. 40
  36. 63
  37. 87
  38. 455
  39. 78
  40. 794

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