Question

Find the surface area of the composite figure.

Answer 1

Answer:

$644cm^2$

Step-by-step explanation:

First we'll work out the surface area of the pink figure.

That's the area of the two 5 by 6 rectangles on the top and bottom, plus the area of the two 5 by 20 and two 6 by 20 rectangles on the sides.

However, we note that the purple figure is blocking out a 6 by 12 section on the pink figure, so we'll need to subtract this.

The above works out to $2\times(30+100+120)-72=428 cm^2$.

Then we'll work out the surface area of the purple figure.

This will be the area of the two 4 by 6 rectangles at the top and bottom, plus the area of the two 4 by 12 and one 6 by 12 rectangles on the sides. Note that there's only one 6 by 12 rectangle because the other face is joined to the pink figure, so it's blocked out.

That's $2\times(24+48)+72=216cm^2$.

So the total surface area is $428+216=644cm^2$.