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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 55 · 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. 1.40 − 19 =
  2. 2.888 − 99 =
  3. 3.39 + 19 =
  4. 4.33 + 19 =
  5. 5.89 − 19 =
  6. 6.53 + 19 =
  7. 7.71 + 9 =
  8. 8.77 − 29 =
  9. 9.41 + 19 =
  10. 10.23 − 9 =
  11. 11.59 − 9 =
  12. 12.688 + 99 =
  13. 13.90 − 29 =
  14. 14.28 + 29 =
  15. 15.719 − 99 =
  16. 16.18 + 19 =
  17. 17.74 + 9 =
  18. 18.47 − 9 =
  19. 19.38 − 9 =
  20. 20.51 + 9 =
  21. 21.68 − 9 =
  22. 22.48 + 19 =
  23. 23.43 − 29 =
  24. 24.213 − 99 =
  25. 25.777 − 99 =
  26. 26.56 + 9 =
  27. 27.106 − 29 =
  28. 28.43 + 29 =
  29. 29.506 + 99 =
  30. 30.458 − 99 =
  31. 31.77 + 19 =
  32. 32.496 − 99 =
  33. 33.35 − 19 =
  34. 34.48 − 9 =
  35. 35.50 − 29 =
  36. 36.48 + 29 =
  37. 37.63 + 9 =
  38. 38.117 + 99 =
  39. 39.21 + 19 =
  40. 40.326 − 99 =

Answer key

  1. 21
  2. 789
  3. 58
  4. 52
  5. 70
  6. 72
  7. 80
  8. 48
  9. 60
  10. 14
  11. 50
  12. 787
  13. 61
  14. 57
  15. 620
  16. 37
  17. 83
  18. 38
  19. 29
  20. 60
  21. 59
  22. 67
  23. 14
  24. 114
  25. 678
  26. 65
  27. 77
  28. 72
  29. 605
  30. 359
  31. 96
  32. 397
  33. 16
  34. 39
  35. 21
  36. 77
  37. 72
  38. 216
  39. 40
  40. 227

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