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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 10 · 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. 1.76 − 9 =
  2. 2.63 − 29 =
  3. 3.792 − 99 =
  4. 4.73 − 9 =
  5. 5.35 + 9 =
  6. 6.59 + 9 =
  7. 7.366 − 99 =
  8. 8.27 + 19 =
  9. 9.79 − 19 =
  10. 10.69 + 9 =
  11. 11.61 − 29 =
  12. 12.572 − 99 =
  13. 13.22 + 9 =
  14. 14.733 − 99 =
  15. 15.29 + 9 =
  16. 16.19 − 9 =
  17. 17.526 + 99 =
  18. 18.70 + 9 =
  19. 19.27 + 9 =
  20. 20.20 + 29 =
  21. 21.63 + 19 =
  22. 22.778 + 99 =
  23. 23.41 + 29 =
  24. 24.39 − 9 =
  25. 25.45 + 9 =
  26. 26.270 − 99 =
  27. 27.27 − 9 =
  28. 28.172 + 99 =
  29. 29.68 + 9 =
  30. 30.87 − 9 =
  31. 31.19 + 29 =
  32. 32.18 + 29 =
  33. 33.72 − 9 =
  34. 34.792 + 99 =
  35. 35.594 − 99 =
  36. 36.104 − 29 =
  37. 37.317 − 99 =
  38. 38.66 − 9 =
  39. 39.538 + 99 =
  40. 40.50 + 29 =

Answer key

  1. 67
  2. 34
  3. 693
  4. 64
  5. 44
  6. 68
  7. 267
  8. 46
  9. 60
  10. 78
  11. 32
  12. 473
  13. 31
  14. 634
  15. 38
  16. 10
  17. 625
  18. 79
  19. 36
  20. 49
  21. 82
  22. 877
  23. 70
  24. 30
  25. 54
  26. 171
  27. 18
  28. 271
  29. 77
  30. 78
  31. 48
  32. 47
  33. 63
  34. 891
  35. 495
  36. 75
  37. 218
  38. 57
  39. 637
  40. 79

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