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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 481 · 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. 1.673 + 99 =
  2. 2.61 − 29 =
  3. 3.39 − 19 =
  4. 4.22 − 9 =
  5. 5.42 + 19 =
  6. 6.38 − 19 =
  7. 7.34 + 19 =
  8. 8.49 + 9 =
  9. 9.175 − 99 =
  10. 10.315 + 99 =
  11. 11.14 + 9 =
  12. 12.73 + 29 =
  13. 13.24 − 9 =
  14. 14.101 − 29 =
  15. 15.43 − 19 =
  16. 16.31 + 9 =
  17. 17.855 − 99 =
  18. 18.59 + 19 =
  19. 19.23 − 9 =
  20. 20.62 + 9 =
  21. 21.50 − 19 =
  22. 22.66 + 9 =
  23. 23.78 − 29 =
  24. 24.564 − 99 =
  25. 25.723 − 99 =
  26. 26.13 − 9 =
  27. 27.51 − 19 =
  28. 28.575 − 99 =
  29. 29.376 + 99 =
  30. 30.12 + 9 =
  31. 31.247 + 99 =
  32. 32.47 + 9 =
  33. 33.62 − 19 =
  34. 34.656 + 99 =
  35. 35.816 − 99 =
  36. 36.75 − 9 =
  37. 37.79 + 9 =
  38. 38.59 + 29 =
  39. 39.18 + 19 =
  40. 40.53 − 29 =

Answer key

  1. 772
  2. 32
  3. 20
  4. 13
  5. 61
  6. 19
  7. 53
  8. 58
  9. 76
  10. 414
  11. 23
  12. 102
  13. 15
  14. 72
  15. 24
  16. 40
  17. 756
  18. 78
  19. 14
  20. 71
  21. 31
  22. 75
  23. 49
  24. 465
  25. 624
  26. 4
  27. 32
  28. 476
  29. 475
  30. 21
  31. 346
  32. 56
  33. 43
  34. 755
  35. 717
  36. 66
  37. 88
  38. 88
  39. 37
  40. 24

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