Question

If ⁿP_r = ⁿP_r+1 and ⁿC_r = ⁿC_r-1, then the value of r is equal to:

(1) 1

(2) 4

(3) 2

(4) 3

Answer 1

Answer is: (3) 2

(1) ⇒ 2r – 1 – r = 1 ⇒ r = 2