Question

If C(n,r): C(n,r +1) = 1 : 2 and C (n,r + 1): C (n, r + 2) = 2:3, determine the value of n and r: (a) (14.4) (b) (12,4) (c) (14,6) (d) None ​

Answer 1

Answer:

option number. a

Step-by-step explanation:

(14.4)

Answer 2

nCr : nCr+1 = 1 : 2 and nCr+1 : nCr+2 = 2 : 3

⇒ 2r + 2 = n – r and 3r + 6 = 2n – 2r – 2 

⇒ n – 3r = 2 and 2n – 5r = 8 

Solving the two simultaneous equations, we get n = 14, r = 4