Answer : Given: ⁿ⁺¹Cr+1 : ⁿCr = 11 : 6 and ⁿCr : ^n–1Cr–1 = 6 : 3

To Find : n & r

We use this property in this question:

⇒6(n+1)=11(r+1)

⇒6n+6=11r+11

⇒6n-11r=5 …(1)

nCr : n–1Cr–1 = 6 : 3

⇒ n=2r…(2)

Using equations 1 & 2 we get

⇒6(2r)-11r=5

⇒12r-11r=5

⇒r=5

⇒n=2×5

⇒n=10

Ans: n =10 & r=5