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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 906 · 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. 1.78 − 19 =
  2. 2.49 − 9 =
  3. 3.18 + 19 =
  4. 4.37 − 9 =
  5. 5.34 + 9 =
  6. 6.59 − 9 =
  7. 7.59 − 29 =
  8. 8.566 − 99 =
  9. 9.99 − 19 =
  10. 10.856 − 99 =
  11. 11.84 − 29 =
  12. 12.63 + 29 =
  13. 13.460 + 99 =
  14. 14.38 − 29 =
  15. 15.55 + 29 =
  16. 16.824 − 99 =
  17. 17.14 + 19 =
  18. 18.418 − 99 =
  19. 19.265 + 99 =
  20. 20.48 − 9 =
  21. 21.76 − 9 =
  22. 22.236 − 99 =
  23. 23.45 − 9 =
  24. 24.41 + 9 =
  25. 25.33 + 29 =
  26. 26.280 + 99 =
  27. 27.47 + 19 =
  28. 28.81 − 19 =
  29. 29.35 − 29 =
  30. 30.61 + 9 =
  31. 31.599 + 99 =
  32. 32.52 + 19 =
  33. 33.25 + 9 =
  34. 34.368 − 99 =
  35. 35.53 − 29 =
  36. 36.71 + 9 =
  37. 37.50 − 19 =
  38. 38.325 − 99 =
  39. 39.60 − 29 =
  40. 40.44 − 29 =

Answer key

  1. 59
  2. 40
  3. 37
  4. 28
  5. 43
  6. 50
  7. 30
  8. 467
  9. 80
  10. 757
  11. 55
  12. 92
  13. 559
  14. 9
  15. 84
  16. 725
  17. 33
  18. 319
  19. 364
  20. 39
  21. 67
  22. 137
  23. 36
  24. 50
  25. 62
  26. 379
  27. 66
  28. 62
  29. 6
  30. 70
  31. 698
  32. 71
  33. 34
  34. 269
  35. 24
  36. 80
  37. 31
  38. 226
  39. 31
  40. 15

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