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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 69 · 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. 1.69 + 9 =
  2. 2.692 − 99 =
  3. 3.68 + 9 =
  4. 4.76 + 29 =
  5. 5.65 + 9 =
  6. 6.59 + 29 =
  7. 7.34 + 9 =
  8. 8.31 + 29 =
  9. 9.563 + 99 =
  10. 10.62 + 19 =
  11. 11.495 − 99 =
  12. 12.244 − 99 =
  13. 13.86 − 9 =
  14. 14.14 + 19 =
  15. 15.49 − 29 =
  16. 16.175 + 99 =
  17. 17.13 − 9 =
  18. 18.88 − 19 =
  19. 19.44 − 29 =
  20. 20.56 + 29 =
  21. 21.39 − 29 =
  22. 22.78 − 9 =
  23. 23.89 − 19 =
  24. 24.40 − 29 =
  25. 25.55 + 9 =
  26. 26.93 − 19 =
  27. 27.125 + 99 =
  28. 28.34 − 29 =
  29. 29.19 − 9 =
  30. 30.68 + 29 =
  31. 31.609 + 99 =
  32. 32.48 + 29 =
  33. 33.33 + 29 =
  34. 34.50 − 19 =
  35. 35.79 + 29 =
  36. 36.66 + 29 =
  37. 37.270 − 99 =
  38. 38.61 + 29 =
  39. 39.54 − 29 =
  40. 40.33 − 29 =

Answer key

  1. 78
  2. 593
  3. 77
  4. 105
  5. 74
  6. 88
  7. 43
  8. 60
  9. 662
  10. 81
  11. 396
  12. 145
  13. 77
  14. 33
  15. 20
  16. 274
  17. 4
  18. 69
  19. 15
  20. 85
  21. 10
  22. 69
  23. 70
  24. 11
  25. 64
  26. 74
  27. 224
  28. 5
  29. 10
  30. 97
  31. 708
  32. 77
  33. 62
  34. 31
  35. 108
  36. 95
  37. 171
  38. 90
  39. 25
  40. 4

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