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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 901 · 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. 1.23 + 19 =
  2. 2.234 − 99 =
  3. 3.65 + 9 =
  4. 4.32 + 9 =
  5. 5.732 + 99 =
  6. 6.39 + 19 =
  7. 7.89 − 29 =
  8. 8.79 + 9 =
  9. 9.48 + 19 =
  10. 10.62 − 29 =
  11. 11.15 + 9 =
  12. 12.12 − 9 =
  13. 13.75 + 29 =
  14. 14.29 + 29 =
  15. 15.55 − 19 =
  16. 16.177 + 99 =
  17. 17.304 + 99 =
  18. 18.85 − 29 =
  19. 19.81 − 9 =
  20. 20.23 − 9 =
  21. 21.44 + 9 =
  22. 22.205 + 99 =
  23. 23.339 + 99 =
  24. 24.62 + 19 =
  25. 25.693 + 99 =
  26. 26.87 − 19 =
  27. 27.12 + 29 =
  28. 28.760 − 99 =
  29. 29.61 − 9 =
  30. 30.552 + 99 =
  31. 31.66 + 9 =
  32. 32.82 − 29 =
  33. 33.32 − 29 =
  34. 34.279 + 99 =
  35. 35.283 + 99 =
  36. 36.318 − 99 =
  37. 37.35 + 19 =
  38. 38.68 − 29 =
  39. 39.65 + 19 =
  40. 40.51 − 9 =

Answer key

  1. 42
  2. 135
  3. 74
  4. 41
  5. 831
  6. 58
  7. 60
  8. 88
  9. 67
  10. 33
  11. 24
  12. 3
  13. 104
  14. 58
  15. 36
  16. 276
  17. 403
  18. 56
  19. 72
  20. 14
  21. 53
  22. 304
  23. 438
  24. 81
  25. 792
  26. 68
  27. 41
  28. 661
  29. 52
  30. 651
  31. 75
  32. 53
  33. 3
  34. 378
  35. 382
  36. 219
  37. 54
  38. 39
  39. 84
  40. 42

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