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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 74 · 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. 1.152 − 99 =
  2. 2.542 − 99 =
  3. 3.88 − 9 =
  4. 4.12 − 9 =
  5. 5.14 + 9 =
  6. 6.46 − 19 =
  7. 7.574 − 99 =
  8. 8.70 + 19 =
  9. 9.37 − 29 =
  10. 10.26 + 29 =
  11. 11.26 − 9 =
  12. 12.62 + 19 =
  13. 13.52 + 29 =
  14. 14.45 − 29 =
  15. 15.641 + 99 =
  16. 16.42 − 9 =
  17. 17.287 − 99 =
  18. 18.67 + 29 =
  19. 19.444 − 99 =
  20. 20.54 − 19 =
  21. 21.46 − 29 =
  22. 22.35 + 19 =
  23. 23.47 + 9 =
  24. 24.697 + 99 =
  25. 25.23 + 19 =
  26. 26.427 − 99 =
  27. 27.732 + 99 =
  28. 28.57 + 29 =
  29. 29.18 − 9 =
  30. 30.393 + 99 =
  31. 31.49 − 9 =
  32. 32.54 − 9 =
  33. 33.63 + 29 =
  34. 34.65 − 19 =
  35. 35.683 + 99 =
  36. 36.284 + 99 =
  37. 37.14 + 29 =
  38. 38.25 + 19 =
  39. 39.19 + 19 =
  40. 40.64 + 9 =

Answer key

  1. 53
  2. 443
  3. 79
  4. 3
  5. 23
  6. 27
  7. 475
  8. 89
  9. 8
  10. 55
  11. 17
  12. 81
  13. 81
  14. 16
  15. 740
  16. 33
  17. 188
  18. 96
  19. 345
  20. 35
  21. 17
  22. 54
  23. 56
  24. 796
  25. 42
  26. 328
  27. 831
  28. 86
  29. 9
  30. 492
  31. 40
  32. 45
  33. 92
  34. 46
  35. 782
  36. 383
  37. 43
  38. 44
  39. 38
  40. 73

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