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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 985 · 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. 1.66 + 19 =
  2. 2.74 + 19 =
  3. 3.24 + 19 =
  4. 4.86 − 9 =
  5. 5.25 + 19 =
  6. 6.37 + 9 =
  7. 7.144 + 99 =
  8. 8.448 + 99 =
  9. 9.40 + 29 =
  10. 10.88 − 9 =
  11. 11.36 + 9 =
  12. 12.50 − 29 =
  13. 13.36 − 29 =
  14. 14.490 + 99 =
  15. 15.81 − 19 =
  16. 16.12 + 29 =
  17. 17.327 + 99 =
  18. 18.81 − 9 =
  19. 19.89 − 9 =
  20. 20.80 − 19 =
  21. 21.42 − 9 =
  22. 22.46 + 9 =
  23. 23.51 − 9 =
  24. 24.71 + 29 =
  25. 25.21 + 19 =
  26. 26.78 + 29 =
  27. 27.82 − 29 =
  28. 28.888 − 99 =
  29. 29.45 − 9 =
  30. 30.45 + 9 =
  31. 31.20 + 19 =
  32. 32.58 − 29 =
  33. 33.19 + 29 =
  34. 34.729 − 99 =
  35. 35.24 − 19 =
  36. 36.435 − 99 =
  37. 37.31 − 9 =
  38. 38.43 + 19 =
  39. 39.43 + 9 =
  40. 40.79 + 9 =

Answer key

  1. 85
  2. 93
  3. 43
  4. 77
  5. 44
  6. 46
  7. 243
  8. 547
  9. 69
  10. 79
  11. 45
  12. 21
  13. 7
  14. 589
  15. 62
  16. 41
  17. 426
  18. 72
  19. 80
  20. 61
  21. 33
  22. 55
  23. 42
  24. 100
  25. 40
  26. 107
  27. 53
  28. 789
  29. 36
  30. 54
  31. 39
  32. 29
  33. 48
  34. 630
  35. 5
  36. 336
  37. 22
  38. 62
  39. 52
  40. 88

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