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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 431 · 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. 1.42 + 29 =
  2. 2.26 + 19 =
  3. 3.72 − 19 =
  4. 4.78 − 9 =
  5. 5.46 − 29 =
  6. 6.594 + 99 =
  7. 7.53 − 29 =
  8. 8.51 − 19 =
  9. 9.22 + 9 =
  10. 10.23 + 29 =
  11. 11.13 + 29 =
  12. 12.25 + 29 =
  13. 13.57 + 29 =
  14. 14.313 + 99 =
  15. 15.62 − 29 =
  16. 16.547 + 99 =
  17. 17.291 + 99 =
  18. 18.52 + 9 =
  19. 19.46 − 19 =
  20. 20.25 − 9 =
  21. 21.19 + 9 =
  22. 22.120 + 99 =
  23. 23.89 − 29 =
  24. 24.593 − 99 =
  25. 25.50 + 9 =
  26. 26.13 − 9 =
  27. 27.67 + 29 =
  28. 28.70 + 9 =
  29. 29.53 − 9 =
  30. 30.79 + 29 =
  31. 31.24 + 9 =
  32. 32.206 − 99 =
  33. 33.79 − 29 =
  34. 34.59 + 19 =
  35. 35.544 + 99 =
  36. 36.30 + 19 =
  37. 37.78 + 19 =
  38. 38.16 + 29 =
  39. 39.14 + 9 =
  40. 40.589 + 99 =

Answer key

  1. 71
  2. 45
  3. 53
  4. 69
  5. 17
  6. 693
  7. 24
  8. 32
  9. 31
  10. 52
  11. 42
  12. 54
  13. 86
  14. 412
  15. 33
  16. 646
  17. 390
  18. 61
  19. 27
  20. 16
  21. 28
  22. 219
  23. 60
  24. 494
  25. 59
  26. 4
  27. 96
  28. 79
  29. 44
  30. 108
  31. 33
  32. 107
  33. 50
  34. 78
  35. 643
  36. 49
  37. 97
  38. 45
  39. 23
  40. 688

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