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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 908 · 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. 1.51 + 19 =
  2. 2.22 + 19 =
  3. 3.50 − 9 =
  4. 4.55 − 9 =
  5. 5.59 − 9 =
  6. 6.48 − 9 =
  7. 7.17 − 9 =
  8. 8.25 − 9 =
  9. 9.53 − 19 =
  10. 10.252 − 99 =
  11. 11.40 − 29 =
  12. 12.40 − 9 =
  13. 13.382 + 99 =
  14. 14.31 + 9 =
  15. 15.662 + 99 =
  16. 16.75 + 29 =
  17. 17.113 + 99 =
  18. 18.23 + 9 =
  19. 19.490 − 99 =
  20. 20.24 + 29 =
  21. 21.30 + 19 =
  22. 22.175 + 99 =
  23. 23.79 + 19 =
  24. 24.704 − 99 =
  25. 25.182 + 99 =
  26. 26.54 − 9 =
  27. 27.73 + 9 =
  28. 28.602 + 99 =
  29. 29.28 + 29 =
  30. 30.77 + 9 =
  31. 31.12 − 9 =
  32. 32.21 + 29 =
  33. 33.41 − 9 =
  34. 34.57 − 19 =
  35. 35.14 + 9 =
  36. 36.73 − 19 =
  37. 37.77 + 29 =
  38. 38.39 + 19 =
  39. 39.80 + 29 =
  40. 40.71 + 29 =

Answer key

  1. 70
  2. 41
  3. 41
  4. 46
  5. 50
  6. 39
  7. 8
  8. 16
  9. 34
  10. 153
  11. 11
  12. 31
  13. 481
  14. 40
  15. 761
  16. 104
  17. 212
  18. 32
  19. 391
  20. 53
  21. 49
  22. 274
  23. 98
  24. 605
  25. 281
  26. 45
  27. 82
  28. 701
  29. 57
  30. 86
  31. 3
  32. 50
  33. 32
  34. 38
  35. 23
  36. 54
  37. 106
  38. 58
  39. 109
  40. 100

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