The formula for the perimeter of a rectangle is:

where 

First find the length.

length or

The length is 

Find the perimeter.

The perimeter is  when the width is .

To find the perimeter of a rectangle, we use the following formula:

where a, b, c, and d are the lengths of the sides of the rectangle.

Now, in the rectangle

we can see the length is 12 feet.  Because it is a rectangle, we know the opposite side is also 12 feet.  We know the width is half of the length.  So, the width is 6 feet.  Because it is a rectangle, the opposite side is also 6 feet.  Knowing this, we can substitute into the formula.  We get

The Smartboard in your math classroom is 3 feet tall and 20 feet long. What is the perimeter of the Smartboard?

We need to find the perimeter of the rectangle that is the Smartboard.

To do so, we simply add up the sides. In this case, we have 2 3ft sides and 2 20 ft sides.

So our answer is 46

Find the distance around a rectangular rug if the rug is 2 feet wide and its length is 3 times the width.

We are really being asked to find the perimeter. To do so, we first need to dimensions.

We are told the width is two feet.

The length is three times the width. 

Now, use the following to find the perimeter:

So our answer is 16 feet

The perimeter of a square is four times the length of a side - here, this is .

The perimeter of a rectangle is twice the sum of its length and its width - here, this is .

The square has perimeter 160, so

The perimeter of the rectangle is .

A rectangular postage stamp has a width of 3 cm and a height of 12 cm. Find the perimeter of the stamp.

To find the perimeter of a rectangle (or any shape) simply add up all the sides.

In this case, we have two sides that are 3 cm and two sides that are 12 cm.

Now, our answer must be in centimeters and not centimeters squared, because we are dealing with perimeter, which is a measure of length.

To find the perimeter of a rectangle, we will use the following formula:

where a, b, c, and d are the lengths of the sides of the rectangle.

Now, we know the width of the rectangle is 6cm.  Because it is a rectangle, we know the opposite side is equal.  Therefore, the opposite side is also 6cm.  

We also know the length is two times the width.  Therefore, the length is 12cm.  Because it is a rectangle, we know the opposite side is equal.  Therefore, the opposite side is also 12cm.

Knowing this, we can substitute into the formula.  We get

To find the perimeter of a rectangle, we will use the following formula:

where a, b, c, and d are the lengths of the sides of the rectangle.

Now, we know the length of the rectangle is 8cm.  Because it is a rectangle, we know the opposite side is also 8cm.  We also know the width is half the length.  Therefore, the width of the rectangle is 4cm.  Because it is a rectangle, we know the opposite side is also 4cm.  Knowing this, we can substitute into the formula.  We get

To find the perimeter of a rectangle, we will use the following formula:

where a, b, c, and d are the lengths of the sides of the rectangle.

Now, we know the width of the rectangle is 4in.  Because it is a rectangle, we know the opposite side is also 4in.  

We know the length is 3 times the width.  Therefore, the length is 12in.  Because it is a rectangle, we know the opposite side is also 12in.  

Knowing all of this, we can substitute into the formula.  We get