CA Foundation · Quantitative Aptitude · Permutations and Combinations
The value of 15C4 + 15C5 equals which of the following?
The sum 15C4 + 15C5 equals 16C5, by Pascal's rule nCr + nC(r-1) = (n+1)Cr. Numerically 1365 + 3003 = 4368, which equals 16C5. The option 16C4 equals 1820 and is incorrect.
- A16C5Correct
- B15C9
- C16C4
- D14C5
Explanation
By Pascal's rule nCr + nC(r-1) = (n+1)Cr, so 15C5 + 15C4 = 16C5. Check: 1365 + 3003 = 4368 = 16C5. 16C4 = 1820, so it is wrong.
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