Question

Find s for the given planes 2x + 2y + sz + 2 = 0 and 3x + y + z – 2 = 0, if they are perpendicular to each other.

(a) 21

(b) – 7

(c) 12

(d) – 8

The question was asked in an interview for job.

The above asked question is from Three Dimensional Geometry in chapter Three Dimensional Geometry of Mathematics – Class 12

Answer 1

Right answer is (d) – 8

Easiest explanation: If their normals are perpendicular to each other then a1a2 + b1b2 + c1c2 = 0.

2(3) + 2(1) + s(1) = 0

s(1) = – 8

k = – 8