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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 605 · 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. 1.31 + 19 =
  2. 2.29 + 19 =
  3. 3.45 + 9 =
  4. 4.64 + 19 =
  5. 5.522 − 99 =
  6. 6.31 − 9 =
  7. 7.71 + 29 =
  8. 8.47 + 29 =
  9. 9.737 − 99 =
  10. 10.461 + 99 =
  11. 11.138 + 99 =
  12. 12.94 − 29 =
  13. 13.845 − 99 =
  14. 14.680 − 99 =
  15. 15.117 + 99 =
  16. 16.58 + 19 =
  17. 17.227 + 99 =
  18. 18.593 − 99 =
  19. 19.55 + 9 =
  20. 20.76 − 9 =
  21. 21.181 − 99 =
  22. 22.33 − 9 =
  23. 23.23 + 9 =
  24. 24.760 − 99 =
  25. 25.51 − 19 =
  26. 26.46 + 9 =
  27. 27.39 + 9 =
  28. 28.706 − 99 =
  29. 29.52 + 29 =
  30. 30.72 − 29 =
  31. 31.748 + 99 =
  32. 32.460 + 99 =
  33. 33.18 + 9 =
  34. 34.38 − 9 =
  35. 35.64 − 9 =
  36. 36.657 + 99 =
  37. 37.78 + 9 =
  38. 38.100 − 29 =
  39. 39.755 + 99 =
  40. 40.67 − 19 =

Answer key

  1. 50
  2. 48
  3. 54
  4. 83
  5. 423
  6. 22
  7. 100
  8. 76
  9. 638
  10. 560
  11. 237
  12. 65
  13. 746
  14. 581
  15. 216
  16. 77
  17. 326
  18. 494
  19. 64
  20. 67
  21. 82
  22. 24
  23. 32
  24. 661
  25. 32
  26. 55
  27. 48
  28. 607
  29. 81
  30. 43
  31. 847
  32. 559
  33. 27
  34. 29
  35. 55
  36. 756
  37. 87
  38. 71
  39. 854
  40. 48

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