geometry/trigonometry
posted by lee pearce .
Triangle ABC is similar to triangle APQ with angle CBA equal to angle QPA and angle A common to both triangles. the length of sides AB, AP and PQ are 90cm,60cm and 30 cm. calculate the length of the side BC

ab/ap = 90/60 = 3/2
so
bc/pq = 3/2
but pq = 30
so
bc = 30 (3/2) = 45 
cheers Damon