Question

A glass prism on a chandelier is 75 millimeters long. A base of the prism is an equilateral triangle with side lengths of 9 millimeters and a height of about 7.8 millimeters. What is the approximate surface area of the prism?

Answer 1

Let's find the area of the equilateral triangle first:

`(1)/(2) *7.8*9`
There are two triangles - one on each end. So we multiply our previous expression by 2.

`(1)/(2) *7.8*9 * 2 \\ =7.8*9`
Each rectangle is 75 millimeters long and 9 millimeters wide: 75*9 mm^2.
We have 3 rectangles each the same size so we multiply 75*9 by 3.
75*9*3 = 2025
2025 + 70.2 = 2095.2