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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 469 · 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. 1.708 − 99 =
  2. 2.652 + 99 =
  3. 3.25 + 19 =
  4. 4.757 + 99 =
  5. 5.37 + 29 =
  6. 6.101 − 29 =
  7. 7.35 − 19 =
  8. 8.17 + 9 =
  9. 9.33 − 19 =
  10. 10.41 − 29 =
  11. 11.63 + 9 =
  12. 12.96 − 19 =
  13. 13.65 − 19 =
  14. 14.84 − 19 =
  15. 15.28 + 19 =
  16. 16.487 − 99 =
  17. 17.26 + 29 =
  18. 18.72 − 19 =
  19. 19.33 − 29 =
  20. 20.24 − 19 =
  21. 21.22 + 9 =
  22. 22.76 − 29 =
  23. 23.733 − 99 =
  24. 24.607 + 99 =
  25. 25.20 + 19 =
  26. 26.93 − 29 =
  27. 27.57 + 9 =
  28. 28.89 − 19 =
  29. 29.74 + 29 =
  30. 30.71 + 19 =
  31. 31.19 + 9 =
  32. 32.24 + 19 =
  33. 33.20 + 9 =
  34. 34.87 − 29 =
  35. 35.71 + 29 =
  36. 36.66 − 9 =
  37. 37.45 + 29 =
  38. 38.29 − 19 =
  39. 39.475 + 99 =
  40. 40.16 + 9 =

Answer key

  1. 609
  2. 751
  3. 44
  4. 856
  5. 66
  6. 72
  7. 16
  8. 26
  9. 14
  10. 12
  11. 72
  12. 77
  13. 46
  14. 65
  15. 47
  16. 388
  17. 55
  18. 53
  19. 4
  20. 5
  21. 31
  22. 47
  23. 634
  24. 706
  25. 39
  26. 64
  27. 66
  28. 70
  29. 103
  30. 90
  31. 28
  32. 43
  33. 29
  34. 58
  35. 100
  36. 57
  37. 74
  38. 10
  39. 574
  40. 25

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