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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 258 · 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. 1.41 − 29 =
  2. 2.29 + 29 =
  3. 3.27 − 19 =
  4. 4.681 + 99 =
  5. 5.13 + 9 =
  6. 6.58 − 29 =
  7. 7.64 + 9 =
  8. 8.49 + 19 =
  9. 9.60 − 19 =
  10. 10.44 + 29 =
  11. 11.70 − 19 =
  12. 12.20 − 9 =
  13. 13.78 + 9 =
  14. 14.102 − 29 =
  15. 15.37 + 29 =
  16. 16.397 + 99 =
  17. 17.80 + 9 =
  18. 18.48 − 29 =
  19. 19.23 + 29 =
  20. 20.30 + 9 =
  21. 21.16 + 9 =
  22. 22.707 + 99 =
  23. 23.422 + 99 =
  24. 24.78 − 29 =
  25. 25.170 − 99 =
  26. 26.62 − 9 =
  27. 27.12 + 29 =
  28. 28.31 − 9 =
  29. 29.66 − 29 =
  30. 30.70 − 9 =
  31. 31.32 − 29 =
  32. 32.364 + 99 =
  33. 33.26 + 29 =
  34. 34.84 − 9 =
  35. 35.52 + 9 =
  36. 36.29 − 19 =
  37. 37.44 + 9 =
  38. 38.199 + 99 =
  39. 39.37 − 19 =
  40. 40.584 − 99 =

Answer key

  1. 12
  2. 58
  3. 8
  4. 780
  5. 22
  6. 29
  7. 73
  8. 68
  9. 41
  10. 73
  11. 51
  12. 11
  13. 87
  14. 73
  15. 66
  16. 496
  17. 89
  18. 19
  19. 52
  20. 39
  21. 25
  22. 806
  23. 521
  24. 49
  25. 71
  26. 53
  27. 41
  28. 22
  29. 37
  30. 61
  31. 3
  32. 463
  33. 55
  34. 75
  35. 61
  36. 10
  37. 53
  38. 298
  39. 18
  40. 485

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