posted by retangular prism on .
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.
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 right-angled?
so the area of one triangle is (1/2)(9)(12) = 54
Add up all the parts