Question

A library building is in the shape of a rectangle. Its floor has a length of (3x + 5) meters and a width of (5x − 1) meters. The expression below represents the area of the floor of the building in square meters:
(3x + 5)(5x − 1)

Which of the following simplified expressions represents the area of the floor of the library building in square meters?

28x − 5
15x2 − 5
15x2 + 28x − 5
15x2 + 22x − 5

Answer 1

The problem says that the expression (3x + 5)(5x − 1) represents the area of the floor of the building in square meters. Therefore,  to solve this problem you have to follow the proccedure shown below.

 1. First, to simplify the expression (3x + 5)(5x − 1) you must apply the distributive property. Then, you obtain:

 15x²-3x+25x-5

 2. Then, you have:

 15x²+22x-5

 3. As you can see, the correct answer is the last option:  15x²+22x-5