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Mathematics - Permutation & Combination Question with Solution | TestHub

MathematicsPermutation & CombinationnPr & nCrMedium2 minQB

MathematicsMediumsingle choice

A guard of 12 men is formed from a group of 'n' soldiers. It is found that 2 particular soldiers A and B are 3 times as often together on guard as 3 particulars soldiers C, D and E. Then (n24) = is equal to

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Answer:

Solution:

$^{n - 2} C_{12 - 2} = 3.^{n - 3} C_{12 - 3}$

$^{n - 2} C_{10} = 3 \cdot^{n - 3} C_{9} \frac{n - 2}{10} = 3 \Rightarrow n = 32$

Stream:JEESubject:MathematicsTopic:Permutation & CombinationSubtopic:nPr & nCr

⏱ 2mℹ️ Source: QB

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