The vectors a and b are given in terms of two perpendicular units vectors i and j on a plane by a = 2i – 3j, b = i + 2j. Find the magnitude of the vector a + 3b

A.
2 
B.
4 
C.
(sqrt{10}) 
D.
35 
E.
2.2
Correct Answer: Option C
Explanation
a = 2i – 3j – 3i + 6j
= i + 3j
= (sqrt{5 times 2})
= (sqrt{10})