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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 982 · 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. 1.72 + 9 =
  2. 2.708 − 99 =
  3. 3.576 + 99 =
  4. 4.62 + 19 =
  5. 5.896 − 99 =
  6. 6.664 − 99 =
  7. 7.389 − 99 =
  8. 8.55 − 29 =
  9. 9.51 − 29 =
  10. 10.60 − 19 =
  11. 11.41 − 9 =
  12. 12.27 + 9 =
  13. 13.56 + 19 =
  14. 14.42 + 29 =
  15. 15.65 − 19 =
  16. 16.40 + 19 =
  17. 17.74 + 29 =
  18. 18.57 − 9 =
  19. 19.70 + 29 =
  20. 20.74 − 29 =
  21. 21.378 + 99 =
  22. 22.43 + 9 =
  23. 23.35 − 19 =
  24. 24.39 + 9 =
  25. 25.15 − 9 =
  26. 26.649 + 99 =
  27. 27.364 + 99 =
  28. 28.370 − 99 =
  29. 29.23 + 19 =
  30. 30.107 − 29 =
  31. 31.76 − 9 =
  32. 32.79 + 9 =
  33. 33.44 + 9 =
  34. 34.95 − 29 =
  35. 35.67 − 19 =
  36. 36.319 + 99 =
  37. 37.37 + 9 =
  38. 38.179 + 99 =
  39. 39.207 − 99 =
  40. 40.50 + 9 =

Answer key

  1. 81
  2. 609
  3. 675
  4. 81
  5. 797
  6. 565
  7. 290
  8. 26
  9. 22
  10. 41
  11. 32
  12. 36
  13. 75
  14. 71
  15. 46
  16. 59
  17. 103
  18. 48
  19. 99
  20. 45
  21. 477
  22. 52
  23. 16
  24. 48
  25. 6
  26. 748
  27. 463
  28. 271
  29. 42
  30. 78
  31. 67
  32. 88
  33. 53
  34. 66
  35. 48
  36. 418
  37. 46
  38. 278
  39. 108
  40. 59

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