Answer: Hi!
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.
Hope this helps!
