If 15Cr : 15Cr – 1 = 11 : 5, find r.

Given:



We know that


And also n! = n(n – 1)(n – 2)…………2.1





5(16 – r) = 11r


80 – 5r = 11r


16r = 80



r = 5


The value of r is 5.


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