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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 626 · 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. 1.277 + 99 =
  2. 2.65 − 19 =
  3. 3.69 − 29 =
  4. 4.66 + 9 =
  5. 5.180 + 99 =
  6. 6.37 + 9 =
  7. 7.650 − 99 =
  8. 8.82 − 9 =
  9. 9.45 + 19 =
  10. 10.104 − 29 =
  11. 11.42 − 19 =
  12. 12.70 − 29 =
  13. 13.44 + 19 =
  14. 14.25 + 9 =
  15. 15.334 − 99 =
  16. 16.18 + 29 =
  17. 17.619 + 99 =
  18. 18.77 − 19 =
  19. 19.71 + 9 =
  20. 20.15 + 19 =
  21. 21.614 + 99 =
  22. 22.60 + 29 =
  23. 23.60 + 9 =
  24. 24.38 + 29 =
  25. 25.69 − 9 =
  26. 26.43 − 9 =
  27. 27.778 + 99 =
  28. 28.53 + 19 =
  29. 29.51 − 29 =
  30. 30.38 + 9 =
  31. 31.66 + 29 =
  32. 32.16 + 9 =
  33. 33.43 − 29 =
  34. 34.834 − 99 =
  35. 35.36 − 19 =
  36. 36.40 − 29 =
  37. 37.71 − 29 =
  38. 38.15 + 9 =
  39. 39.607 + 99 =
  40. 40.80 − 29 =

Answer key

  1. 376
  2. 46
  3. 40
  4. 75
  5. 279
  6. 46
  7. 551
  8. 73
  9. 64
  10. 75
  11. 23
  12. 41
  13. 63
  14. 34
  15. 235
  16. 47
  17. 718
  18. 58
  19. 80
  20. 34
  21. 713
  22. 89
  23. 69
  24. 67
  25. 60
  26. 34
  27. 877
  28. 72
  29. 22
  30. 47
  31. 95
  32. 25
  33. 14
  34. 735
  35. 17
  36. 11
  37. 42
  38. 24
  39. 706
  40. 51

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