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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 20 · 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. 1.62 + 9 =
  2. 2.31 + 19 =
  3. 3.62 − 29 =
  4. 4.309 + 99 =
  5. 5.225 + 99 =
  6. 6.397 + 99 =
  7. 7.32 + 19 =
  8. 8.89 − 19 =
  9. 9.442 + 99 =
  10. 10.30 + 19 =
  11. 11.62 + 19 =
  12. 12.21 + 9 =
  13. 13.75 − 9 =
  14. 14.691 + 99 =
  15. 15.27 + 29 =
  16. 16.636 + 99 =
  17. 17.86 − 19 =
  18. 18.626 + 99 =
  19. 19.451 + 99 =
  20. 20.66 + 9 =
  21. 21.172 − 99 =
  22. 22.464 − 99 =
  23. 23.76 + 19 =
  24. 24.886 − 99 =
  25. 25.25 + 19 =
  26. 26.26 + 19 =
  27. 27.29 − 19 =
  28. 28.68 − 9 =
  29. 29.49 + 19 =
  30. 30.43 + 9 =
  31. 31.82 − 29 =
  32. 32.586 + 99 =
  33. 33.16 + 9 =
  34. 34.78 − 9 =
  35. 35.36 + 19 =
  36. 36.18 + 29 =
  37. 37.226 + 99 =
  38. 38.80 + 19 =
  39. 39.27 − 19 =
  40. 40.83 − 9 =

Answer key

  1. 71
  2. 50
  3. 33
  4. 408
  5. 324
  6. 496
  7. 51
  8. 70
  9. 541
  10. 49
  11. 81
  12. 30
  13. 66
  14. 790
  15. 56
  16. 735
  17. 67
  18. 725
  19. 550
  20. 75
  21. 73
  22. 365
  23. 95
  24. 787
  25. 44
  26. 45
  27. 10
  28. 59
  29. 68
  30. 52
  31. 53
  32. 685
  33. 25
  34. 69
  35. 55
  36. 47
  37. 325
  38. 99
  39. 8
  40. 74

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