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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 93 · 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. 1.53 − 29 =
  2. 2.14 − 9 =
  3. 3.629 − 99 =
  4. 4.65 − 29 =
  5. 5.54 + 9 =
  6. 6.64 − 9 =
  7. 7.716 + 99 =
  8. 8.877 − 99 =
  9. 9.40 + 29 =
  10. 10.82 − 19 =
  11. 11.42 − 29 =
  12. 12.35 + 19 =
  13. 13.27 + 19 =
  14. 14.28 − 19 =
  15. 15.660 − 99 =
  16. 16.44 − 19 =
  17. 17.72 + 29 =
  18. 18.61 + 19 =
  19. 19.26 + 9 =
  20. 20.96 − 19 =
  21. 21.49 + 19 =
  22. 22.42 − 9 =
  23. 23.79 + 9 =
  24. 24.63 + 29 =
  25. 25.23 − 19 =
  26. 26.670 − 99 =
  27. 27.31 + 9 =
  28. 28.108 + 99 =
  29. 29.872 − 99 =
  30. 30.436 + 99 =
  31. 31.75 − 9 =
  32. 32.67 + 19 =
  33. 33.68 + 19 =
  34. 34.510 − 99 =
  35. 35.59 + 19 =
  36. 36.81 − 9 =
  37. 37.15 + 29 =
  38. 38.68 + 9 =
  39. 39.43 + 19 =
  40. 40.61 + 29 =

Answer key

  1. 24
  2. 5
  3. 530
  4. 36
  5. 63
  6. 55
  7. 815
  8. 778
  9. 69
  10. 63
  11. 13
  12. 54
  13. 46
  14. 9
  15. 561
  16. 25
  17. 101
  18. 80
  19. 35
  20. 77
  21. 68
  22. 33
  23. 88
  24. 92
  25. 4
  26. 571
  27. 40
  28. 207
  29. 773
  30. 535
  31. 66
  32. 86
  33. 87
  34. 411
  35. 78
  36. 72
  37. 44
  38. 77
  39. 62
  40. 90

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