Vector homework question - multiple answer

Question

I received a multiple answer question on my homework with the following question:

Find the y-coordinate of a vector that has the length 5 and is perpendicular to the vector a→ = (-6 -8).

The answer possibilities were

A) 4

B) 8

C) 0.8

D) 3

I personally calculated 3 by turning a into a perpendicular vector and then into a unit vector to give it the length 1, then finally multiplying it by 5 to get the right vector with the right length. That gave me the y-coordinate of 3 but apparently it says it is wrong?

Answer 1

Yes, you're method is sound and the answer is correct. I would say that the answer is +/- 3 for v_y as the vector can be perpendicular in two directions. The phrase, "y-coordinate" bothers me as it should be the y component of the vector of magnitude 5 that is perpendicular to ,<-6,-8>