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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 365 · 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. 1.867 − 99 =
  2. 2.28 + 9 =
  3. 3.12 + 29 =
  4. 4.82 − 19 =
  5. 5.448 + 99 =
  6. 6.41 + 9 =
  7. 7.24 − 19 =
  8. 8.48 + 19 =
  9. 9.675 − 99 =
  10. 10.74 + 19 =
  11. 11.349 + 99 =
  12. 12.690 + 99 =
  13. 13.29 − 9 =
  14. 14.43 − 9 =
  15. 15.55 − 9 =
  16. 16.52 + 19 =
  17. 17.577 + 99 =
  18. 18.60 + 29 =
  19. 19.38 − 19 =
  20. 20.19 + 9 =
  21. 21.61 − 9 =
  22. 22.32 − 19 =
  23. 23.63 + 9 =
  24. 24.26 + 9 =
  25. 25.44 + 19 =
  26. 26.207 + 99 =
  27. 27.15 + 19 =
  28. 28.43 − 19 =
  29. 29.76 + 9 =
  30. 30.37 − 19 =
  31. 31.512 − 99 =
  32. 32.319 + 99 =
  33. 33.64 − 19 =
  34. 34.173 + 99 =
  35. 35.726 + 99 =
  36. 36.76 − 29 =
  37. 37.25 − 19 =
  38. 38.58 + 9 =
  39. 39.32 + 19 =
  40. 40.38 + 29 =

Answer key

  1. 768
  2. 37
  3. 41
  4. 63
  5. 547
  6. 50
  7. 5
  8. 67
  9. 576
  10. 93
  11. 448
  12. 789
  13. 20
  14. 34
  15. 46
  16. 71
  17. 676
  18. 89
  19. 19
  20. 28
  21. 52
  22. 13
  23. 72
  24. 35
  25. 63
  26. 306
  27. 34
  28. 24
  29. 85
  30. 18
  31. 413
  32. 418
  33. 45
  34. 272
  35. 825
  36. 47
  37. 6
  38. 67
  39. 51
  40. 67

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