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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 765 · 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. 1.32 + 29 =
  2. 2.521 + 99 =
  3. 3.701 + 99 =
  4. 4.22 + 19 =
  5. 5.357 + 99 =
  6. 6.31 + 29 =
  7. 7.35 − 19 =
  8. 8.57 − 9 =
  9. 9.48 + 19 =
  10. 10.671 − 99 =
  11. 11.89 − 29 =
  12. 12.137 + 99 =
  13. 13.19 − 9 =
  14. 14.740 + 99 =
  15. 15.55 + 19 =
  16. 16.60 + 19 =
  17. 17.27 − 19 =
  18. 18.84 − 9 =
  19. 19.28 + 9 =
  20. 20.41 + 19 =
  21. 21.721 − 99 =
  22. 22.809 − 99 =
  23. 23.320 − 99 =
  24. 24.67 + 9 =
  25. 25.76 + 9 =
  26. 26.607 + 99 =
  27. 27.41 − 19 =
  28. 28.28 − 9 =
  29. 29.734 − 99 =
  30. 30.22 − 9 =
  31. 31.14 + 29 =
  32. 32.454 − 99 =
  33. 33.15 + 19 =
  34. 34.24 + 19 =
  35. 35.56 + 9 =
  36. 36.30 + 9 =
  37. 37.57 + 29 =
  38. 38.49 + 9 =
  39. 39.39 + 29 =
  40. 40.565 − 99 =

Answer key

  1. 61
  2. 620
  3. 800
  4. 41
  5. 456
  6. 60
  7. 16
  8. 48
  9. 67
  10. 572
  11. 60
  12. 236
  13. 10
  14. 839
  15. 74
  16. 79
  17. 8
  18. 75
  19. 37
  20. 60
  21. 622
  22. 710
  23. 221
  24. 76
  25. 85
  26. 706
  27. 22
  28. 19
  29. 635
  30. 13
  31. 43
  32. 355
  33. 34
  34. 43
  35. 65
  36. 39
  37. 86
  38. 58
  39. 68
  40. 466

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