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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 387 · 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. 1.118 + 99 =
  2. 2.74 + 29 =
  3. 3.62 + 9 =
  4. 4.23 + 9 =
  5. 5.72 + 29 =
  6. 6.45 − 29 =
  7. 7.39 + 9 =
  8. 8.37 + 9 =
  9. 9.55 − 29 =
  10. 10.40 − 19 =
  11. 11.242 + 99 =
  12. 12.49 − 29 =
  13. 13.89 − 29 =
  14. 14.28 − 19 =
  15. 15.53 − 19 =
  16. 16.31 + 19 =
  17. 17.362 + 99 =
  18. 18.42 − 29 =
  19. 19.76 + 29 =
  20. 20.90 − 29 =
  21. 21.23 − 9 =
  22. 22.52 − 19 =
  23. 23.47 + 19 =
  24. 24.453 − 99 =
  25. 25.80 + 9 =
  26. 26.66 + 9 =
  27. 27.82 − 9 =
  28. 28.104 − 29 =
  29. 29.25 + 9 =
  30. 30.42 + 29 =
  31. 31.83 − 29 =
  32. 32.655 + 99 =
  33. 33.774 − 99 =
  34. 34.43 + 9 =
  35. 35.79 − 9 =
  36. 36.33 − 29 =
  37. 37.51 + 29 =
  38. 38.27 − 9 =
  39. 39.73 + 29 =
  40. 40.68 + 29 =

Answer key

  1. 217
  2. 103
  3. 71
  4. 32
  5. 101
  6. 16
  7. 48
  8. 46
  9. 26
  10. 21
  11. 341
  12. 20
  13. 60
  14. 9
  15. 34
  16. 50
  17. 461
  18. 13
  19. 105
  20. 61
  21. 14
  22. 33
  23. 66
  24. 354
  25. 89
  26. 75
  27. 73
  28. 75
  29. 34
  30. 71
  31. 54
  32. 754
  33. 675
  34. 52
  35. 70
  36. 4
  37. 80
  38. 18
  39. 102
  40. 97

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