There are three different rectangles that make up this closed box. We need to calculate the area of them to find the surface area of this shape. Here are the measurements:
Rectangle 1: 40 * 20
Rectangle 2: 50 * 20
Rectangle 3: 50 * 40
Note that there are two of each type of rectangle, so when we are done calculating the area of each rectangle we will multiply each by 2.
Rectangle 1: 40 * 20 = 800(2) = 1600
Rectangle 2: 50 * 20 = 1000(2) = 2000
Rectangle 3: 50 * 40 = 2000(2) - 4000
Now, we add the areas together: 1600 + 2000 + 4000 = 7600
The surface area of this closed box is 7600cm squared.
The answer is 10.2. Since it's a percentage, you move the decimal two places to the left which gives you 0.12. Then, you multiply that by 85 and you get 10.2.
