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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 433 · 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. 1.82 − 29 =
  2. 2.606 − 99 =
  3. 3.48 + 19 =
  4. 4.22 − 19 =
  5. 5.225 + 99 =
  6. 6.685 + 99 =
  7. 7.303 + 99 =
  8. 8.601 + 99 =
  9. 9.743 + 99 =
  10. 10.561 − 99 =
  11. 11.709 + 99 =
  12. 12.25 − 9 =
  13. 13.54 + 29 =
  14. 14.509 + 99 =
  15. 15.89 − 29 =
  16. 16.461 + 99 =
  17. 17.357 + 99 =
  18. 18.38 + 9 =
  19. 19.23 + 19 =
  20. 20.156 + 99 =
  21. 21.80 + 9 =
  22. 22.72 + 29 =
  23. 23.592 + 99 =
  24. 24.419 + 99 =
  25. 25.49 + 9 =
  26. 26.31 + 9 =
  27. 27.25 + 9 =
  28. 28.66 − 9 =
  29. 29.404 + 99 =
  30. 30.37 + 19 =
  31. 31.47 + 29 =
  32. 32.565 + 99 =
  33. 33.77 + 19 =
  34. 34.72 + 9 =
  35. 35.52 + 9 =
  36. 36.452 + 99 =
  37. 37.53 + 19 =
  38. 38.78 + 9 =
  39. 39.52 + 19 =
  40. 40.43 − 19 =

Answer key

  1. 53
  2. 507
  3. 67
  4. 3
  5. 324
  6. 784
  7. 402
  8. 700
  9. 842
  10. 462
  11. 808
  12. 16
  13. 83
  14. 608
  15. 60
  16. 560
  17. 456
  18. 47
  19. 42
  20. 255
  21. 89
  22. 101
  23. 691
  24. 518
  25. 58
  26. 40
  27. 34
  28. 57
  29. 503
  30. 56
  31. 76
  32. 664
  33. 96
  34. 81
  35. 61
  36. 551
  37. 72
  38. 87
  39. 71
  40. 24

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