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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 932 · 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. 1.222 − 99 =
  2. 2.217 − 99 =
  3. 3.37 + 19 =
  4. 4.69 − 9 =
  5. 5.66 − 9 =
  6. 6.13 + 29 =
  7. 7.339 + 99 =
  8. 8.767 − 99 =
  9. 9.33 − 19 =
  10. 10.30 + 9 =
  11. 11.61 + 29 =
  12. 12.60 + 19 =
  13. 13.36 − 19 =
  14. 14.72 − 19 =
  15. 15.40 + 9 =
  16. 16.20 − 9 =
  17. 17.34 − 9 =
  18. 18.594 + 99 =
  19. 19.703 + 99 =
  20. 20.837 − 99 =
  21. 21.65 − 19 =
  22. 22.75 + 29 =
  23. 23.69 + 19 =
  24. 24.762 − 99 =
  25. 25.62 − 9 =
  26. 26.32 + 19 =
  27. 27.854 − 99 =
  28. 28.284 − 99 =
  29. 29.90 − 19 =
  30. 30.49 + 19 =
  31. 31.52 − 19 =
  32. 32.74 − 9 =
  33. 33.96 − 19 =
  34. 34.73 + 29 =
  35. 35.67 − 9 =
  36. 36.629 − 99 =
  37. 37.72 + 19 =
  38. 38.67 − 19 =
  39. 39.84 − 9 =
  40. 40.104 − 29 =

Answer key

  1. 123
  2. 118
  3. 56
  4. 60
  5. 57
  6. 42
  7. 438
  8. 668
  9. 14
  10. 39
  11. 90
  12. 79
  13. 17
  14. 53
  15. 49
  16. 11
  17. 25
  18. 693
  19. 802
  20. 738
  21. 46
  22. 104
  23. 88
  24. 663
  25. 53
  26. 51
  27. 755
  28. 185
  29. 71
  30. 68
  31. 33
  32. 65
  33. 77
  34. 102
  35. 58
  36. 530
  37. 91
  38. 48
  39. 75
  40. 75

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