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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 394 · 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. 1.67 − 19 =
  2. 2.47 + 9 =
  3. 3.74 + 19 =
  4. 4.33 + 19 =
  5. 5.38 + 9 =
  6. 6.65 + 29 =
  7. 7.245 − 99 =
  8. 8.631 + 99 =
  9. 9.49 + 19 =
  10. 10.78 − 9 =
  11. 11.213 + 99 =
  12. 12.53 + 19 =
  13. 13.109 − 29 =
  14. 14.538 − 99 =
  15. 15.720 − 99 =
  16. 16.77 − 19 =
  17. 17.56 + 19 =
  18. 18.44 + 19 =
  19. 19.16 − 9 =
  20. 20.81 − 29 =
  21. 21.78 + 9 =
  22. 22.63 − 9 =
  23. 23.55 − 19 =
  24. 24.856 − 99 =
  25. 25.59 − 9 =
  26. 26.67 + 29 =
  27. 27.27 − 9 =
  28. 28.75 + 19 =
  29. 29.61 + 9 =
  30. 30.29 + 9 =
  31. 31.65 + 9 =
  32. 32.91 − 19 =
  33. 33.746 + 99 =
  34. 34.56 − 19 =
  35. 35.41 − 19 =
  36. 36.634 − 99 =
  37. 37.162 − 99 =
  38. 38.73 + 9 =
  39. 39.20 + 19 =
  40. 40.566 + 99 =

Answer key

  1. 48
  2. 56
  3. 93
  4. 52
  5. 47
  6. 94
  7. 146
  8. 730
  9. 68
  10. 69
  11. 312
  12. 72
  13. 80
  14. 439
  15. 621
  16. 58
  17. 75
  18. 63
  19. 7
  20. 52
  21. 87
  22. 54
  23. 36
  24. 757
  25. 50
  26. 96
  27. 18
  28. 94
  29. 70
  30. 38
  31. 74
  32. 72
  33. 845
  34. 37
  35. 22
  36. 535
  37. 63
  38. 82
  39. 39
  40. 665

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