Posted by retangular prism on Wednesday, March 28, 2012 at 1:36am.
the base of a solid right prism is a triangle whose sides are 9cm, 12cm and 15cm. The height of the prism is 5cm. Then the total surface area of the prism is.

maths  Reiny, Wednesday, March 28, 2012 at 8:26am
The surface area = 2 triangles + 3 rectangles
the area of the rectangles is easy
5(9) + 5(12) + (15)
for the area of the triangle, did you notice
15^ = 9^2+12^2 making it rightangled?
so the area of one triangle is (1/2)(9)(12) = 54
Add up all the parts