CA Foundation · Quantitative Aptitude · Permutations and Combinations
What is the value of 7! ÷ (4! × 3!)?
The value is 35. Cancelling 4! from 7! leaves 7 × 6 × 5 = 210, and dividing this by 3! = 6 gives 35. This is the same as the combination 7C3. The option 210 forgets to divide by 3!.
- A30
- B35Correct
- C42
- D210
Explanation
7! = 5040, 4! = 24 and 3! = 6, so 24 × 6 = 144... compute by cancelling instead: 7!/4! = 7 × 6 × 5 = 210. Then 210 ÷ 3! = 210 ÷ 6 = 35. The value 210 results from forgetting to divide by 3!.
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