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CA Foundation · Quantitative Aptitude · Permutations and Combinations

The value of 10!/(8!) − 9!/(7!) is:

The value is 18. Since 10!/8! = 10 × 9 = 90 and 9!/7! = 9 × 8 = 72, subtracting gives 90 − 72 = 18. Each ratio is simplified by cancelling the common factorial part.

  1. A18Correct
  2. B90
  3. C72
  4. D8

Explanation

10!/8! = 10 × 9 = 90. 9!/7! = 9 × 8 = 72. The difference is 90 − 72 = 18. Option 72 would result from using only the second term.

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