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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 332 · 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. 1.19 − 9 =
  2. 2.764 + 99 =
  3. 3.32 − 19 =
  4. 4.75 + 9 =
  5. 5.74 + 19 =
  6. 6.42 − 29 =
  7. 7.719 + 99 =
  8. 8.628 + 99 =
  9. 9.14 + 9 =
  10. 10.26 + 19 =
  11. 11.52 + 9 =
  12. 12.72 + 9 =
  13. 13.48 − 29 =
  14. 14.75 + 19 =
  15. 15.152 − 99 =
  16. 16.74 + 9 =
  17. 17.17 + 9 =
  18. 18.68 + 29 =
  19. 19.684 + 99 =
  20. 20.54 + 29 =
  21. 21.632 + 99 =
  22. 22.18 + 9 =
  23. 23.35 + 9 =
  24. 24.76 + 29 =
  25. 25.13 + 29 =
  26. 26.63 + 19 =
  27. 27.46 + 9 =
  28. 28.69 − 19 =
  29. 29.395 + 99 =
  30. 30.37 + 29 =
  31. 31.65 − 19 =
  32. 32.45 − 29 =
  33. 33.57 + 9 =
  34. 34.531 + 99 =
  35. 35.34 + 29 =
  36. 36.67 + 19 =
  37. 37.28 − 19 =
  38. 38.56 − 9 =
  39. 39.675 − 99 =
  40. 40.611 + 99 =

Answer key

  1. 10
  2. 863
  3. 13
  4. 84
  5. 93
  6. 13
  7. 818
  8. 727
  9. 23
  10. 45
  11. 61
  12. 81
  13. 19
  14. 94
  15. 53
  16. 83
  17. 26
  18. 97
  19. 783
  20. 83
  21. 731
  22. 27
  23. 44
  24. 105
  25. 42
  26. 82
  27. 55
  28. 50
  29. 494
  30. 66
  31. 46
  32. 16
  33. 66
  34. 630
  35. 63
  36. 86
  37. 9
  38. 47
  39. 576
  40. 710

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