1. The problem statement, all variables and given/known data ABCD is a square (AB = AD = BC = CD). The point P and Q are located in the middle of BC and CD. If AP and AD is expressed by the name vector a and b, then AQ = ... A) (1/2)a + (3/4)b B) (1/3)a + (2/3)b C) (3/4)a + (1/2)b D) (2/3)a + (1/3)b E) (2/3)a + (3/4)b 2. Relevant equations Vector addition law (still confused) 3. The attempt at a solution This problem comes in a competition about 4 months ago. I just chose the answer A (random guessing) and thank God the answer is A. But how do we find it?