If matrix P has order 4x2 and matrix Q has the order 2x1. what is order of matrix PQ?

4x1

Step-by-step explanation:

if the columns of P = the ropes of Q you can multiply PQ and the resultant matrix is order (rows of P) x (columns of Q)

you have 4x2 * 2x1. since the 2's in the middle match the answer is a 4x1