If a rectangle has a length of 10 and a width of 5, what is the perimeter?

To find the perimeter of a rectangle, the formula used is P = 2(length + width). In this case, the length is 10 and the width is 5.

First, you would add the length and the width together:

10 + 5 = 15.

Next, you multiply that sum by 2 to find the perimeter:

2 * 15 = 30.

Thus, the perimeter of the rectangle is 30. This calculation clearly demonstrates how to use the formula for the perimeter of a rectangle effectively, leading to the conclusion that option B is indeed the correct answer.