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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 802 · 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. 1.58 − 19 =
  2. 2.68 − 19 =
  3. 3.15 + 9 =
  4. 4.59 − 19 =
  5. 5.70 + 9 =
  6. 6.311 − 99 =
  7. 7.603 + 99 =
  8. 8.25 + 9 =
  9. 9.43 + 19 =
  10. 10.52 − 19 =
  11. 11.385 + 99 =
  12. 12.348 + 99 =
  13. 13.49 + 19 =
  14. 14.48 + 29 =
  15. 15.581 − 99 =
  16. 16.24 − 19 =
  17. 17.74 − 19 =
  18. 18.21 + 29 =
  19. 19.68 + 9 =
  20. 20.21 + 9 =
  21. 21.618 + 99 =
  22. 22.20 + 9 =
  23. 23.75 + 9 =
  24. 24.17 − 9 =
  25. 25.280 + 99 =
  26. 26.895 − 99 =
  27. 27.92 − 19 =
  28. 28.583 + 99 =
  29. 29.74 + 19 =
  30. 30.69 + 29 =
  31. 31.794 + 99 =
  32. 32.66 + 9 =
  33. 33.54 − 29 =
  34. 34.37 + 19 =
  35. 35.32 − 19 =
  36. 36.77 + 29 =
  37. 37.65 + 19 =
  38. 38.28 − 19 =
  39. 39.32 − 9 =
  40. 40.29 − 19 =

Answer key

  1. 39
  2. 49
  3. 24
  4. 40
  5. 79
  6. 212
  7. 702
  8. 34
  9. 62
  10. 33
  11. 484
  12. 447
  13. 68
  14. 77
  15. 482
  16. 5
  17. 55
  18. 50
  19. 77
  20. 30
  21. 717
  22. 29
  23. 84
  24. 8
  25. 379
  26. 796
  27. 73
  28. 682
  29. 93
  30. 98
  31. 893
  32. 75
  33. 25
  34. 56
  35. 13
  36. 106
  37. 84
  38. 9
  39. 23
  40. 10

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