For your friend's birthday, you have 3 presents to wrap. find the combined surface area of these 3 gifts so you know how much wrapping paper you will need.

The answer is: 5,614 square inches.

The explanation is shown below:

1. The gift on the bottom is a rectangular prism. To calculate its surface area, you must apply the following formula:

Where is the length (20 inches), is the width (42 inches) and is the heigth (16 inches).

2. Substitute values:

3. The surface area of the other gifts can be calculated with the formula for calculate the surface area of a cube:

Where is the side.

4. The surface area of the bigger cube is:

5. The surface area of the smaller cube is:

6. The total surface area (the combined surface area of the three gifts) is:

- 1.613 = -1.6 or -1.61

-1.522 = -1.5 or -1.52

0.587 = 0.6 or 0.59

3.079 = 3.1 or 3.08