JEE MATHEMATICS MCQ: COMBINATIONS

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The number of ways of selecting 4 letters from 3 'a's, 4 'b's and 5 'c's is

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Correct option: A

\frac{{ }^8 \mathrm{C}_2}{2}

Correct Answer:

\frac{{ }^8 \mathrm{C}_2}{2}

is incorrect. The correct answer is 77. The number of ways to select 4 letters is found by considering all possible combinations of a's, b's, and c's, taking into account the available quantities of each letter.

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{\;^{n + 2}}{C_8}:{\;^{n - 2}}{P_4} = \frac{{57}}{{16}}

, then

n

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