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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 820 · 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. 1.822 − 99 =
  2. 2.30 − 19 =
  3. 3.80 + 9 =
  4. 4.594 + 99 =
  5. 5.187 + 99 =
  6. 6.63 − 9 =
  7. 7.660 − 99 =
  8. 8.24 + 9 =
  9. 9.668 + 99 =
  10. 10.33 − 9 =
  11. 11.92 − 19 =
  12. 12.64 − 19 =
  13. 13.97 − 29 =
  14. 14.739 − 99 =
  15. 15.27 + 29 =
  16. 16.48 − 29 =
  17. 17.487 + 99 =
  18. 18.36 + 9 =
  19. 19.26 − 19 =
  20. 20.12 + 9 =
  21. 21.88 − 9 =
  22. 22.65 + 29 =
  23. 23.219 + 99 =
  24. 24.64 + 19 =
  25. 25.76 − 19 =
  26. 26.73 + 9 =
  27. 27.58 − 19 =
  28. 28.64 + 29 =
  29. 29.38 − 29 =
  30. 30.16 + 9 =
  31. 31.62 − 19 =
  32. 32.75 + 9 =
  33. 33.17 − 9 =
  34. 34.65 − 19 =
  35. 35.81 − 9 =
  36. 36.79 − 29 =
  37. 37.66 − 19 =
  38. 38.50 − 29 =
  39. 39.36 − 19 =
  40. 40.17 + 9 =

Answer key

  1. 723
  2. 11
  3. 89
  4. 693
  5. 286
  6. 54
  7. 561
  8. 33
  9. 767
  10. 24
  11. 73
  12. 45
  13. 68
  14. 640
  15. 56
  16. 19
  17. 586
  18. 45
  19. 7
  20. 21
  21. 79
  22. 94
  23. 318
  24. 83
  25. 57
  26. 82
  27. 39
  28. 93
  29. 9
  30. 25
  31. 43
  32. 84
  33. 8
  34. 46
  35. 72
  36. 50
  37. 47
  38. 21
  39. 17
  40. 26

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