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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 868 · 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. 1.66 + 29 =
  2. 2.52 − 19 =
  3. 3.12 + 29 =
  4. 4.41 − 19 =
  5. 5.74 + 9 =
  6. 6.65 − 19 =
  7. 7.75 + 19 =
  8. 8.68 + 19 =
  9. 9.93 − 29 =
  10. 10.13 + 29 =
  11. 11.273 − 99 =
  12. 12.26 − 19 =
  13. 13.30 − 9 =
  14. 14.395 + 99 =
  15. 15.80 + 19 =
  16. 16.40 − 19 =
  17. 17.49 + 19 =
  18. 18.244 + 99 =
  19. 19.55 − 9 =
  20. 20.422 + 99 =
  21. 21.35 − 19 =
  22. 22.65 + 19 =
  23. 23.25 + 29 =
  24. 24.27 − 19 =
  25. 25.79 + 9 =
  26. 26.70 + 19 =
  27. 27.688 + 99 =
  28. 28.38 + 9 =
  29. 29.67 + 9 =
  30. 30.896 − 99 =
  31. 31.99 − 19 =
  32. 32.97 − 29 =
  33. 33.42 + 19 =
  34. 34.72 + 9 =
  35. 35.86 − 29 =
  36. 36.98 − 19 =
  37. 37.587 + 99 =
  38. 38.57 + 9 =
  39. 39.522 − 99 =
  40. 40.23 − 9 =

Answer key

  1. 95
  2. 33
  3. 41
  4. 22
  5. 83
  6. 46
  7. 94
  8. 87
  9. 64
  10. 42
  11. 174
  12. 7
  13. 21
  14. 494
  15. 99
  16. 21
  17. 68
  18. 343
  19. 46
  20. 521
  21. 16
  22. 84
  23. 54
  24. 8
  25. 88
  26. 89
  27. 787
  28. 47
  29. 76
  30. 797
  31. 80
  32. 68
  33. 61
  34. 81
  35. 57
  36. 79
  37. 686
  38. 66
  39. 423
  40. 14

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