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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 450 · 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. 1.71 + 19 =
  2. 2.32 − 29 =
  3. 3.58 + 19 =
  4. 4.707 + 99 =
  5. 5.31 + 19 =
  6. 6.64 − 29 =
  7. 7.38 − 9 =
  8. 8.66 + 9 =
  9. 9.13 − 9 =
  10. 10.12 + 19 =
  11. 11.83 − 19 =
  12. 12.21 + 9 =
  13. 13.65 + 9 =
  14. 14.74 − 9 =
  15. 15.23 − 9 =
  16. 16.49 + 19 =
  17. 17.36 − 29 =
  18. 18.189 − 99 =
  19. 19.22 + 29 =
  20. 20.88 − 19 =
  21. 21.25 + 29 =
  22. 22.473 − 99 =
  23. 23.407 + 99 =
  24. 24.387 + 99 =
  25. 25.44 + 19 =
  26. 26.32 − 19 =
  27. 27.90 − 29 =
  28. 28.98 − 19 =
  29. 29.52 + 29 =
  30. 30.81 − 29 =
  31. 31.86 − 19 =
  32. 32.41 + 9 =
  33. 33.41 − 9 =
  34. 34.52 + 9 =
  35. 35.81 − 9 =
  36. 36.66 + 19 =
  37. 37.267 − 99 =
  38. 38.60 − 19 =
  39. 39.585 − 99 =
  40. 40.26 + 9 =

Answer key

  1. 90
  2. 3
  3. 77
  4. 806
  5. 50
  6. 35
  7. 29
  8. 75
  9. 4
  10. 31
  11. 64
  12. 30
  13. 74
  14. 65
  15. 14
  16. 68
  17. 7
  18. 90
  19. 51
  20. 69
  21. 54
  22. 374
  23. 506
  24. 486
  25. 63
  26. 13
  27. 61
  28. 79
  29. 81
  30. 52
  31. 67
  32. 50
  33. 32
  34. 61
  35. 72
  36. 85
  37. 168
  38. 41
  39. 486
  40. 35

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