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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 73 · 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. 1.747 + 99 =
  2. 2.36 − 19 =
  3. 3.259 − 99 =
  4. 4.18 − 9 =
  5. 5.24 + 9 =
  6. 6.29 + 9 =
  7. 7.40 − 9 =
  8. 8.26 + 9 =
  9. 9.25 + 9 =
  10. 10.633 − 99 =
  11. 11.79 − 9 =
  12. 12.67 − 29 =
  13. 13.76 + 29 =
  14. 14.13 + 29 =
  15. 15.187 − 99 =
  16. 16.18 + 9 =
  17. 17.176 + 99 =
  18. 18.24 + 19 =
  19. 19.18 + 29 =
  20. 20.786 − 99 =
  21. 21.621 + 99 =
  22. 22.76 + 9 =
  23. 23.22 + 19 =
  24. 24.76 − 29 =
  25. 25.101 − 29 =
  26. 26.79 − 19 =
  27. 27.31 + 19 =
  28. 28.44 + 19 =
  29. 29.71 + 9 =
  30. 30.42 − 9 =
  31. 31.407 − 99 =
  32. 32.40 + 9 =
  33. 33.38 + 19 =
  34. 34.66 + 19 =
  35. 35.15 + 19 =
  36. 36.80 − 19 =
  37. 37.55 + 19 =
  38. 38.481 − 99 =
  39. 39.29 − 19 =
  40. 40.54 − 29 =

Answer key

  1. 846
  2. 17
  3. 160
  4. 9
  5. 33
  6. 38
  7. 31
  8. 35
  9. 34
  10. 534
  11. 70
  12. 38
  13. 105
  14. 42
  15. 88
  16. 27
  17. 275
  18. 43
  19. 47
  20. 687
  21. 720
  22. 85
  23. 41
  24. 47
  25. 72
  26. 60
  27. 50
  28. 63
  29. 80
  30. 33
  31. 308
  32. 49
  33. 57
  34. 85
  35. 34
  36. 61
  37. 74
  38. 382
  39. 10
  40. 25

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