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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 210 · 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. 1.14 + 9 =
  2. 2.23 − 9 =
  3. 3.716 − 99 =
  4. 4.361 − 99 =
  5. 5.358 + 99 =
  6. 6.71 − 29 =
  7. 7.282 + 99 =
  8. 8.87 − 19 =
  9. 9.67 − 19 =
  10. 10.45 − 29 =
  11. 11.52 + 19 =
  12. 12.13 − 9 =
  13. 13.25 + 19 =
  14. 14.46 + 29 =
  15. 15.47 + 19 =
  16. 16.28 + 19 =
  17. 17.73 − 19 =
  18. 18.53 − 29 =
  19. 19.84 − 9 =
  20. 20.407 − 99 =
  21. 21.497 + 99 =
  22. 22.39 − 29 =
  23. 23.25 − 9 =
  24. 24.43 + 9 =
  25. 25.58 − 29 =
  26. 26.56 + 9 =
  27. 27.81 − 19 =
  28. 28.14 − 9 =
  29. 29.492 + 99 =
  30. 30.87 − 9 =
  31. 31.35 + 9 =
  32. 32.79 − 9 =
  33. 33.323 + 99 =
  34. 34.74 − 19 =
  35. 35.315 − 99 =
  36. 36.26 + 9 =
  37. 37.832 − 99 =
  38. 38.22 − 9 =
  39. 39.55 − 29 =
  40. 40.85 − 29 =

Answer key

  1. 23
  2. 14
  3. 617
  4. 262
  5. 457
  6. 42
  7. 381
  8. 68
  9. 48
  10. 16
  11. 71
  12. 4
  13. 44
  14. 75
  15. 66
  16. 47
  17. 54
  18. 24
  19. 75
  20. 308
  21. 596
  22. 10
  23. 16
  24. 52
  25. 29
  26. 65
  27. 62
  28. 5
  29. 591
  30. 78
  31. 44
  32. 70
  33. 422
  34. 55
  35. 216
  36. 35
  37. 733
  38. 13
  39. 26
  40. 56

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