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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 740 · 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. 1.69 − 19 =
  2. 2.517 − 99 =
  3. 3.295 + 99 =
  4. 4.54 + 9 =
  5. 5.31 − 9 =
  6. 6.56 + 9 =
  7. 7.192 + 99 =
  8. 8.40 − 19 =
  9. 9.442 − 99 =
  10. 10.15 + 9 =
  11. 11.23 + 9 =
  12. 12.96 − 29 =
  13. 13.34 − 19 =
  14. 14.23 − 9 =
  15. 15.668 + 99 =
  16. 16.47 + 19 =
  17. 17.39 − 9 =
  18. 18.25 + 9 =
  19. 19.41 + 9 =
  20. 20.591 + 99 =
  21. 21.39 − 29 =
  22. 22.60 + 29 =
  23. 23.660 − 99 =
  24. 24.54 + 29 =
  25. 25.105 − 29 =
  26. 26.617 − 99 =
  27. 27.95 − 19 =
  28. 28.13 + 29 =
  29. 29.38 + 19 =
  30. 30.51 − 9 =
  31. 31.35 + 9 =
  32. 32.56 − 19 =
  33. 33.332 − 99 =
  34. 34.41 − 29 =
  35. 35.19 − 9 =
  36. 36.24 − 9 =
  37. 37.553 − 99 =
  38. 38.25 − 19 =
  39. 39.60 + 9 =
  40. 40.24 + 29 =

Answer key

  1. 50
  2. 418
  3. 394
  4. 63
  5. 22
  6. 65
  7. 291
  8. 21
  9. 343
  10. 24
  11. 32
  12. 67
  13. 15
  14. 14
  15. 767
  16. 66
  17. 30
  18. 34
  19. 50
  20. 690
  21. 10
  22. 89
  23. 561
  24. 83
  25. 76
  26. 518
  27. 76
  28. 42
  29. 57
  30. 42
  31. 44
  32. 37
  33. 233
  34. 12
  35. 10
  36. 15
  37. 454
  38. 6
  39. 69
  40. 53

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