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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 637 · 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. 1.61 − 19 =
  2. 2.245 − 99 =
  3. 3.79 + 19 =
  4. 4.522 − 99 =
  5. 5.89 − 19 =
  6. 6.69 + 19 =
  7. 7.43 − 9 =
  8. 8.76 + 29 =
  9. 9.62 + 19 =
  10. 10.73 + 9 =
  11. 11.672 + 99 =
  12. 12.738 + 99 =
  13. 13.62 − 19 =
  14. 14.29 + 19 =
  15. 15.36 + 29 =
  16. 16.15 + 9 =
  17. 17.24 + 9 =
  18. 18.40 − 29 =
  19. 19.547 − 99 =
  20. 20.40 + 19 =
  21. 21.65 + 29 =
  22. 22.16 + 9 =
  23. 23.57 + 9 =
  24. 24.32 + 9 =
  25. 25.14 + 29 =
  26. 26.50 − 9 =
  27. 27.46 + 9 =
  28. 28.79 + 9 =
  29. 29.680 − 99 =
  30. 30.500 − 99 =
  31. 31.25 + 9 =
  32. 32.96 − 19 =
  33. 33.83 − 29 =
  34. 34.48 − 9 =
  35. 35.241 + 99 =
  36. 36.33 + 29 =
  37. 37.54 + 9 =
  38. 38.63 − 19 =
  39. 39.73 + 29 =
  40. 40.81 − 9 =

Answer key

  1. 42
  2. 146
  3. 98
  4. 423
  5. 70
  6. 88
  7. 34
  8. 105
  9. 81
  10. 82
  11. 771
  12. 837
  13. 43
  14. 48
  15. 65
  16. 24
  17. 33
  18. 11
  19. 448
  20. 59
  21. 94
  22. 25
  23. 66
  24. 41
  25. 43
  26. 41
  27. 55
  28. 88
  29. 581
  30. 401
  31. 34
  32. 77
  33. 54
  34. 39
  35. 340
  36. 62
  37. 63
  38. 44
  39. 102
  40. 72

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