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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 578 · 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. 1.157 − 99 =
  2. 2.37 + 9 =
  3. 3.66 − 29 =
  4. 4.507 − 99 =
  5. 5.100 − 29 =
  6. 6.72 + 19 =
  7. 7.19 + 9 =
  8. 8.59 + 29 =
  9. 9.36 − 29 =
  10. 10.56 + 19 =
  11. 11.631 − 99 =
  12. 12.56 + 9 =
  13. 13.27 − 9 =
  14. 14.91 − 29 =
  15. 15.12 + 19 =
  16. 16.29 + 9 =
  17. 17.75 − 29 =
  18. 18.78 + 9 =
  19. 19.15 + 29 =
  20. 20.27 + 9 =
  21. 21.712 − 99 =
  22. 22.22 + 19 =
  23. 23.28 + 9 =
  24. 24.229 − 99 =
  25. 25.77 − 19 =
  26. 26.35 − 19 =
  27. 27.16 − 9 =
  28. 28.256 + 99 =
  29. 29.75 + 9 =
  30. 30.505 + 99 =
  31. 31.594 + 99 =
  32. 32.84 − 9 =
  33. 33.81 − 9 =
  34. 34.51 − 29 =
  35. 35.462 + 99 =
  36. 36.29 − 19 =
  37. 37.498 − 99 =
  38. 38.37 + 19 =
  39. 39.55 − 29 =
  40. 40.50 − 29 =

Answer key

  1. 58
  2. 46
  3. 37
  4. 408
  5. 71
  6. 91
  7. 28
  8. 88
  9. 7
  10. 75
  11. 532
  12. 65
  13. 18
  14. 62
  15. 31
  16. 38
  17. 46
  18. 87
  19. 44
  20. 36
  21. 613
  22. 41
  23. 37
  24. 130
  25. 58
  26. 16
  27. 7
  28. 355
  29. 84
  30. 604
  31. 693
  32. 75
  33. 72
  34. 22
  35. 561
  36. 10
  37. 399
  38. 56
  39. 26
  40. 21

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