1.

If vector a = vector(4 i + 3 j + 4 k) and vector b = vector(3 i + 2 k) then |vector(b x 2a)| is(A) 18 (B) 20 (C) 22 (D) 25

Answer»

Correct option:

(C) 22 

vec(b×2a)

=2vec(3i+2k)×vec(4i+3j+4k)

=2vec(12i×i+8k×i+9i×j+6k×j+12i×k+8k×k)

=2vec(12.0+8j+9k-6i-12j+8*0)

=2vec(-6i-4j+9k)

Now |(b×2a)|

=2√(6^2+4^2+9^2)=2√133

~23


Discussion

No Comment Found

Related InterviewSolutions