Mathematics - Permutation & Combination Question with Solution | TestHub

MathematicsPermutation & CombinationnPr & nCrEasy2 minPYQ_2011

MathematicsEasysingle choice

If $^{20} C_{r} =^{20} C_{r - 10}$ then $^{18} C_{r}$ is equal to

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Answer:

Solution:

$^{20} C_{r} =^{20} C_{r - 10} \Rightarrow r + (r - 10) = 20 \Rightarrow r = 15$ $∴^{18} C_{r} =^{18} C_{15} =^{18} C_{3} = \frac{18 \cdot 17 \cdot 16}{1 \cdot 2 \cdot 3} = 816$

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

⏱ 2mℹ️ Source: PYQ_2011

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