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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 663 · 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. 1.486 − 99 =
  2. 2.63 + 19 =
  3. 3.26 − 19 =
  4. 4.26 + 9 =
  5. 5.20 + 19 =
  6. 6.696 − 99 =
  7. 7.35 + 9 =
  8. 8.46 + 9 =
  9. 9.494 + 99 =
  10. 10.76 − 19 =
  11. 11.52 + 29 =
  12. 12.106 − 29 =
  13. 13.739 − 99 =
  14. 14.76 + 19 =
  15. 15.670 − 99 =
  16. 16.73 + 9 =
  17. 17.48 − 19 =
  18. 18.21 + 9 =
  19. 19.77 + 29 =
  20. 20.25 + 29 =
  21. 21.651 + 99 =
  22. 22.14 + 9 =
  23. 23.21 + 29 =
  24. 24.190 + 99 =
  25. 25.297 − 99 =
  26. 26.45 − 9 =
  27. 27.62 + 9 =
  28. 28.94 − 19 =
  29. 29.83 − 9 =
  30. 30.33 − 19 =
  31. 31.85 − 9 =
  32. 32.55 − 29 =
  33. 33.19 + 9 =
  34. 34.47 − 9 =
  35. 35.23 + 29 =
  36. 36.16 − 9 =
  37. 37.82 − 19 =
  38. 38.885 − 99 =
  39. 39.58 + 19 =
  40. 40.57 − 29 =

Answer key

  1. 387
  2. 82
  3. 7
  4. 35
  5. 39
  6. 597
  7. 44
  8. 55
  9. 593
  10. 57
  11. 81
  12. 77
  13. 640
  14. 95
  15. 571
  16. 82
  17. 29
  18. 30
  19. 106
  20. 54
  21. 750
  22. 23
  23. 50
  24. 289
  25. 198
  26. 36
  27. 71
  28. 75
  29. 74
  30. 14
  31. 76
  32. 26
  33. 28
  34. 38
  35. 52
  36. 7
  37. 63
  38. 786
  39. 77
  40. 28

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