The perimeter of a rectangle is found by adding up the length of all four sides. Since the two long sides are 12 cm, and the two shorter sides are 7 cm the perimeter can be found by:

\(\displaystyle 12+12+7+7=38\)

The perimeter is 38 cm.

To find the perimeter of a rectangle, add the lengths of the rectangle's four sides. If you have only the width and the height, then you can easily find all four sides (two sides are each equal to the height and the other two sides are equal to the width).  Multiply both the height and width by two and add the results.

\(\displaystyle (2\cdot 9)+(2\cdot 7)=32\)

For a rectangle, area is \(\displaystyle A = lw\) and perimeter is \(\displaystyle P=2l+2w\), where \(\displaystyle l\) is the length and \(\displaystyle w\) is the width.

Let \(\displaystyle x\) = length and \(\displaystyle x-4\) = width.

The area equation to solve becomes \(\displaystyle x(x-4)=96\), or \(\displaystyle x^{2}-4x-96=0\).

To factor, find two numbers the sum to -4 and multiply to -96.  -12 and 8 will work:

x² + 8x - 12x - 96 = 0

x(x + 8) - 12(x + 8) = 0

(x - 12)(x + 8) = 0

Set each factor equal to zero and solve:

\(\displaystyle x=12\) or \(\displaystyle x=-8\).

Therefore the length is \(\displaystyle 12\; cm\) and the width is \(\displaystyle 8 \; cm\), giving a perimeter of \(\displaystyle 40\; cm\).

Convert the dimensions from yards to feet by multiplying by 3: This makes the dimensions 600 feet and 1,200 feet. The perimeter of this farm is therefore

\(\displaystyle P = 600+600+1,200+1,200= 3,600 \;\textrm{ft}\).

Multiply this by the cost of the fence per foot:

\(\displaystyle 3,600 \cdot \$1.75 = \$ 6,300\)

To find the perimeter of any rectangle, add all of the sides up:

20 + 20 + 12 + 12 = 64 inches

You could use this formula as well:

\(\displaystyle P=2l+2w\), where P = perimeter,  l = length, w = width

This formula comes from the fact that there are 2 lengths and 2 widths in every rectangle.

\(\displaystyle P=2(20)+2(12)\)

\(\displaystyle P=64 \text{ inches}\)

Remember, the perimeter of the rectangle is the sum of all four sides:

\(\displaystyle P=6+24+A+B\)

It is obvious from the figure that A=6 and B=24.

\(\displaystyle P=6+24+6+24=60\)

Divide the area of the rectangle by the width in order to find the length of 14 feet. The perimeter is the sum of the side lengths, which in this case is 14 feet + 4 feet +14 feet + 4 feet, or 36 feet.

The area of a rectangle is the width times the height, and we are told that in this rectangle the width is two times the height.

Therefore, \(\displaystyle A = W \times H ; W = 2H\).

Plug in the value of the area:

\(\displaystyle 32 in^{^{2}} = W \times 2W=2W^{2}\)

Solve for \(\displaystyle W\) to find a width of 4 inches. Using our formula above, the height must be 8 inches.  We then add all the sides of the rectangle together to find the perimeter:

\(\displaystyle 8+8+4+4=24\ in.\)

Let l be the length of the garden and w be the width. 

By the specifications of the problem, l = 2w-3.

Plug this in for length in the area formula:

A = l  x w = (2w - 3) x w = 9

Solve for the width:

2w²- 3w - 9 =0 

(2w + 3)(w - 3) = 0

w is either 3 or -3/2, but we can't have a negative width, so w = 3.

If w = 3, then length = 2(3) - 3 = 3.

Now plug the width and length into the formula for perimeter:

P = 2 l + 2w = 2(3) + 2(3) = 12

Recall how to find the perimeter of a rectangle:

\(\displaystyle \text{Perimeter}= 2(\text{length}+\text{width})\)

For the given rectangle,

\(\displaystyle \text{Perimeter}=2 (12+3)=2(15)=30\)