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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 921 · 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 + 29 =
  2. 2.68 + 9 =
  3. 3.27 − 19 =
  4. 4.87 − 9 =
  5. 5.38 + 29 =
  6. 6.99 − 29 =
  7. 7.46 + 9 =
  8. 8.56 + 29 =
  9. 9.36 − 29 =
  10. 10.90 − 19 =
  11. 11.852 − 99 =
  12. 12.831 − 99 =
  13. 13.58 + 19 =
  14. 14.61 + 19 =
  15. 15.801 − 99 =
  16. 16.215 + 99 =
  17. 17.71 − 29 =
  18. 18.59 + 19 =
  19. 19.30 + 19 =
  20. 20.451 + 99 =
  21. 21.173 + 99 =
  22. 22.51 − 19 =
  23. 23.18 − 9 =
  24. 24.691 − 99 =
  25. 25.94 − 19 =
  26. 26.176 − 99 =
  27. 27.415 + 99 =
  28. 28.19 + 9 =
  29. 29.33 + 19 =
  30. 30.86 − 29 =
  31. 31.24 + 19 =
  32. 32.244 − 99 =
  33. 33.24 + 29 =
  34. 34.750 − 99 =
  35. 35.60 − 29 =
  36. 36.20 + 19 =
  37. 37.351 − 99 =
  38. 38.44 − 9 =
  39. 39.42 − 9 =
  40. 40.44 − 19 =

Answer key

  1. 95
  2. 77
  3. 8
  4. 78
  5. 67
  6. 70
  7. 55
  8. 85
  9. 7
  10. 71
  11. 753
  12. 732
  13. 77
  14. 80
  15. 702
  16. 314
  17. 42
  18. 78
  19. 49
  20. 550
  21. 272
  22. 32
  23. 9
  24. 592
  25. 75
  26. 77
  27. 514
  28. 28
  29. 52
  30. 57
  31. 43
  32. 145
  33. 53
  34. 651
  35. 31
  36. 39
  37. 252
  38. 35
  39. 33
  40. 25

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