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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 997 · 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. 1.23 − 9 =
  2. 2.57 + 9 =
  3. 3.70 + 29 =
  4. 4.24 − 9 =
  5. 5.42 + 19 =
  6. 6.23 + 19 =
  7. 7.74 + 29 =
  8. 8.72 + 29 =
  9. 9.93 − 19 =
  10. 10.105 − 29 =
  11. 11.69 + 9 =
  12. 12.31 − 9 =
  13. 13.13 + 29 =
  14. 14.56 + 9 =
  15. 15.760 − 99 =
  16. 16.40 + 9 =
  17. 17.59 + 9 =
  18. 18.46 − 29 =
  19. 19.74 − 9 =
  20. 20.49 + 9 =
  21. 21.17 + 19 =
  22. 22.526 − 99 =
  23. 23.14 + 19 =
  24. 24.79 − 9 =
  25. 25.44 + 29 =
  26. 26.31 + 29 =
  27. 27.84 − 29 =
  28. 28.77 + 19 =
  29. 29.23 + 29 =
  30. 30.262 + 99 =
  31. 31.75 + 9 =
  32. 32.107 + 99 =
  33. 33.344 + 99 =
  34. 34.82 − 29 =
  35. 35.511 + 99 =
  36. 36.22 + 29 =
  37. 37.272 + 99 =
  38. 38.83 − 19 =
  39. 39.76 − 9 =
  40. 40.103 − 29 =

Answer key

  1. 14
  2. 66
  3. 99
  4. 15
  5. 61
  6. 42
  7. 103
  8. 101
  9. 74
  10. 76
  11. 78
  12. 22
  13. 42
  14. 65
  15. 661
  16. 49
  17. 68
  18. 17
  19. 65
  20. 58
  21. 36
  22. 427
  23. 33
  24. 70
  25. 73
  26. 60
  27. 55
  28. 96
  29. 52
  30. 361
  31. 84
  32. 206
  33. 443
  34. 53
  35. 610
  36. 51
  37. 371
  38. 64
  39. 67
  40. 74

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