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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 702 · 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. 1.797 − 99 =
  2. 2.501 − 99 =
  3. 3.439 + 99 =
  4. 4.357 − 99 =
  5. 5.49 − 9 =
  6. 6.381 − 99 =
  7. 7.232 + 99 =
  8. 8.65 + 19 =
  9. 9.33 + 9 =
  10. 10.279 − 99 =
  11. 11.88 − 9 =
  12. 12.29 + 9 =
  13. 13.35 + 29 =
  14. 14.31 − 19 =
  15. 15.64 − 29 =
  16. 16.74 + 29 =
  17. 17.23 + 19 =
  18. 18.76 − 29 =
  19. 19.48 + 19 =
  20. 20.15 + 19 =
  21. 21.83 − 9 =
  22. 22.87 − 19 =
  23. 23.12 + 19 =
  24. 24.32 + 19 =
  25. 25.63 + 9 =
  26. 26.24 + 19 =
  27. 27.245 − 99 =
  28. 28.55 + 29 =
  29. 29.240 + 99 =
  30. 30.70 + 19 =
  31. 31.75 − 19 =
  32. 32.574 + 99 =
  33. 33.281 − 99 =
  34. 34.19 − 9 =
  35. 35.37 − 9 =
  36. 36.16 + 9 =
  37. 37.28 − 19 =
  38. 38.13 + 9 =
  39. 39.45 + 19 =
  40. 40.829 − 99 =

Answer key

  1. 698
  2. 402
  3. 538
  4. 258
  5. 40
  6. 282
  7. 331
  8. 84
  9. 42
  10. 180
  11. 79
  12. 38
  13. 64
  14. 12
  15. 35
  16. 103
  17. 42
  18. 47
  19. 67
  20. 34
  21. 74
  22. 68
  23. 31
  24. 51
  25. 72
  26. 43
  27. 146
  28. 84
  29. 339
  30. 89
  31. 56
  32. 673
  33. 182
  34. 10
  35. 28
  36. 25
  37. 9
  38. 22
  39. 64
  40. 730

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