There is not enough information given to solve the problem. I have given a similar problem below which is solvable. Were the triangles similar? If so you did not state that they were. Were they right triangles? If so you did not state that they were. Something was given that you forgot to state. If you will state the problem exactly as it was given to you in the thank-you note below, I'll be happy to help you with it. Here is a possaible rewording: Right triangle ABC is similar to Right triangle PQR. M is the mid point of BC and N is the mid point of QR. if the area of Right triangle ABC = 100 sq cm, and the area of right triangle PQR = 144 sq cm. if AB is 4cm then PN is........? Could that be the problem you were given? Edwin