Assertion: If the lines `(x-1)/(-3)=(y-2)/(2k)=(z-3)/2 and (x-1)/(3k)=(y-1)/1=(z-6)/(-5) ` are perpendicular to each other , then `k=10/7`, Reason: Two lines having diection ratios `l_1,m_1,n_1 and l_2,m_2,n_2` are perpendiculr to each other if and only if `l_1l_2+m_1m_2+n_1n_2=0` (A) Both A and R are true and R is the correct explanation of A (B) Both A and R are true R is not te correct explanation of A (C) A is true but R is false. (D) A is false but R is true.

A. `(-5)/(7)`

B. `(5)/(7)`

C. `(10)/(7)`

D. `(-10)/(7)`

A. `(-5)/(7)`

B. `(5)/(7)`

C. `(10)/(7)`

D. `(-10)/(7)`

Correct Answer – D

Since the given lines are are perpendicular to each other we have ,

`(-3) (3k) +(2kxx1) +2xx (-5) =0 rArr 7k =-10 rArr k = (-10)/(7)`