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If ^14Cr = 14 and ^15Cr = 15. Find the value of ^14Cr-1.(a) 1(b) 14(c) 15(d) 3The question was posed to me by my college director while I was bunking the class.I would like to ask this question from Combinations topic in chapter Permutations and Combinations of Mathematics – Class 11

Answer»

The correct ANSWER is (a) 1

For explanation I WOULD SAY: We know, ^nCr + ^nCr-1 = ^n+1Cr

Substituting n=14 and r=4, we GET ^14Cr + ^14Cr-1 = ^15Cr

=>^14Cr-1 = ^15Cr – ^14Cr = 15-14 = 1.



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