HSPT Math - How to find the perimeter of a figure

What is the perimeter of the equilateral triangle below?

Screen shot 2015 11 09 at 8.59.58 am

Explanation

An equilateral triangle means that all of the side lengths are the same. To find the perimeter, we can take the one known side length and multiply by (since there are sides) or we can add the side length to itself times.

$9\times3=27$

What is the perimeter of a square with a side legnth of 8?

Explanation

When searching for the perimeter of a square we are looking for the sum of the lengths of all of the sides enclosing the figure. In this case there are four sides that are all equal length. To find the perimeter we add all four of them together or multiply the side length by four.

In this example the equation looks like this:

Multiply the numbers together to get .

What is the perimeter of the triangle below?

Screen shot 2015 11 09 at 8.17.56 am

Explanation

To find the perimeter, we add all of the side lengths together.

What is the perimeter of the polygon below?

Explanation

To find the area of a perimeter, we add all of the side lengths together.

What is the perimeter of the polygon below?

Explanation

To find the area of a perimeter, we add all of the side lengths together.

Rectangle 2

Note: Figure NOT drawn to scale.

The above rectangle has area 18. Give its perimeter.

$17\frac{15}{26}$

$8\frac{41}{52}$

$18\frac{11}{16}$

$47\frac{15}{16}$

Explanation

The product of the length and the width of a rectangle is its area, so to find the length, divide the area by the width:

$L = A \div W = 18 \div 3\frac{1}{4} = \frac{18}{1} \div \frac{13}{4} = \frac{18}{1} \cdot \frac{4} {13} = \frac{72}{13}$

We can use $L = \frac{72}{13}$ and $W = 3\frac{1}{4} = \frac{13}{4}$ to find the perimeter by adding each of these twice:

$P = \frac{72}{13} + \frac{13}{4} + \frac{72}{13} + \frac{13}{4}$

$P = \frac{288}{52} + \frac{169}{52} +\frac{288}{52} + \frac{169}{52}$

$P = \frac{914}{52} = \frac{457}{26} = 17\frac{15}{26}$

What is the perimeter of the polygon below?

Explanation

To find the area of a perimeter, we add all of the side lengths together.

What is the circumference of a circle with a radius of 5?

$\dpi{100} 10\pi$

$\dpi{100} 25\pi$

$\dpi{100} 5\pi$

$\dpi{100} 50\pi$

Explanation

The formula for circumference is $\dpi{100} \pi d$ or $\dpi{100} 2\pi r$ .

Since we are given the radius, we will use $\dpi{100} 2\pi r$ .

$\dpi{100} 2\pi r=2\pi (5)=10\pi$

What is the perimeter of a figure with seven sides, four of which measure 9 inches, two of which measure 10 inches, and one of which measures a foot?

Explanation

Add the side measures, in inches (changing one foot to 12 inches):

Square X has 3 times the area of Square Y. If the perimeter of Square Y is 24 ft, what is the area of Square X, in sq ft?

112

144

108

Explanation

Find the area of Square Y, then calculate the area of Square X.

If the perimeter of Square Y is 24, then each side is 24/4, or 6.

A = 6 * 6 = 36 sq ft, for Square Y

If Square X has 3 times the area, then 3 * 36 = 108 sq ft.

How to find the perimeter of a figure

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