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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 389 · 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. 1.562 − 99 =
  2. 2.116 + 99 =
  3. 3.66 + 29 =
  4. 4.63 − 9 =
  5. 5.20 + 19 =
  6. 6.602 − 99 =
  7. 7.30 − 9 =
  8. 8.96 − 19 =
  9. 9.329 + 99 =
  10. 10.265 + 99 =
  11. 11.41 + 29 =
  12. 12.65 + 9 =
  13. 13.44 + 29 =
  14. 14.49 + 19 =
  15. 15.46 − 19 =
  16. 16.28 − 9 =
  17. 17.75 − 29 =
  18. 18.30 + 9 =
  19. 19.42 + 19 =
  20. 20.62 − 29 =
  21. 21.752 − 99 =
  22. 22.18 + 19 =
  23. 23.46 − 29 =
  24. 24.674 − 99 =
  25. 25.74 + 9 =
  26. 26.98 − 19 =
  27. 27.746 + 99 =
  28. 28.12 + 9 =
  29. 29.64 + 9 =
  30. 30.667 − 99 =
  31. 31.61 + 9 =
  32. 32.655 + 99 =
  33. 33.74 + 19 =
  34. 34.80 + 19 =
  35. 35.82 − 9 =
  36. 36.33 − 29 =
  37. 37.52 + 9 =
  38. 38.21 + 19 =
  39. 39.46 + 9 =
  40. 40.34 − 29 =

Answer key

  1. 463
  2. 215
  3. 95
  4. 54
  5. 39
  6. 503
  7. 21
  8. 77
  9. 428
  10. 364
  11. 70
  12. 74
  13. 73
  14. 68
  15. 27
  16. 19
  17. 46
  18. 39
  19. 61
  20. 33
  21. 653
  22. 37
  23. 17
  24. 575
  25. 83
  26. 79
  27. 845
  28. 21
  29. 73
  30. 568
  31. 70
  32. 754
  33. 93
  34. 99
  35. 73
  36. 4
  37. 61
  38. 40
  39. 55
  40. 5

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