CA Foundation · Quantitative Aptitude · Permutations and Combinations
What is the value of 7! / (5! × 2!)?
The value is 21. Writing 7! as 7 × 6 × 5! cancels 5!, leaving 42 divided by 2! which is 2, giving 21. This is the same as 7C2, the number of ways to choose 2 items from 7.
- A14
- B21Correct
- C42
- D10
Explanation
7! = 7 × 6 × 5!, so 7!/(5! × 2!) = (7 × 6)/2 = 21. Option 42 results from forgetting to divide by 2!. This equals 7C2 = 21.
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