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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 747 · 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 − 19 =
  2. 2.54 − 29 =
  3. 3.472 + 99 =
  4. 4.42 + 29 =
  5. 5.882 − 99 =
  6. 6.40 − 29 =
  7. 7.784 − 99 =
  8. 8.93 − 29 =
  9. 9.76 + 9 =
  10. 10.43 − 29 =
  11. 11.53 + 19 =
  12. 12.69 − 29 =
  13. 13.20 − 9 =
  14. 14.36 + 19 =
  15. 15.318 + 99 =
  16. 16.62 − 9 =
  17. 17.52 + 19 =
  18. 18.49 + 19 =
  19. 19.84 − 29 =
  20. 20.50 − 9 =
  21. 21.33 − 9 =
  22. 22.209 + 99 =
  23. 23.226 + 99 =
  24. 24.531 + 99 =
  25. 25.38 − 9 =
  26. 26.23 + 29 =
  27. 27.24 + 19 =
  28. 28.412 + 99 =
  29. 29.33 + 19 =
  30. 30.41 + 19 =
  31. 31.19 + 29 =
  32. 32.79 + 19 =
  33. 33.594 + 99 =
  34. 34.14 − 9 =
  35. 35.68 − 19 =
  36. 36.37 − 29 =
  37. 37.13 + 9 =
  38. 38.53 + 29 =
  39. 39.53 − 29 =
  40. 40.47 − 19 =

Answer key

  1. 43
  2. 25
  3. 571
  4. 71
  5. 783
  6. 11
  7. 685
  8. 64
  9. 85
  10. 14
  11. 72
  12. 40
  13. 11
  14. 55
  15. 417
  16. 53
  17. 71
  18. 68
  19. 55
  20. 41
  21. 24
  22. 308
  23. 325
  24. 630
  25. 29
  26. 52
  27. 43
  28. 511
  29. 52
  30. 60
  31. 48
  32. 98
  33. 693
  34. 5
  35. 49
  36. 8
  37. 22
  38. 82
  39. 24
  40. 28

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