# SSAT Elementary Level Math : How to find the perimeter of a triangle

## Example Questions

### Example Question #11 : How To Find The Perimeter Of A Triangle

The perimeter of an isosceles triangle is 22 mm. Which choice shows the correct side lengths of the triangle?

Possible Answers:

Correct answer:

Explanation:

An isosceles triangle has two equal sides, and one different side. All of the answer choices add up to 22 mm, but only one choice shows two equal sides and one different side that add up to 22mm.

### Example Question #12 : How To Find The Perimeter Of A Triangle

An equilateral triangle is a type of triangle that has sides that are each of the same length. If one of the sides of an equilateral triangle is  units long, what is the perimeter of the triangle?

Possible Answers:

units

units

units

units

units

Correct answer:

units

Explanation:

Since an equilateral triangle has three equal sides, the total perimeter of the triangle is  units, since each side is  units long and .

### Example Question #13 : How To Find The Perimeter Of A Triangle

A triangle has sides of three different lengths. One of its sides is  units long. Another of its sides is  units long. The third side is of a length that is the average of its other two sides. What is the perimeter of this triangle?

Possible Answers:

Correct answer:

Explanation:

We know two of the lengths of the triangle's sides:  and . We are also told that its third side's length is an average of its other two sides. We can find the average of  and  by adding them together and dividing by two:  and , so the triangle's third side has a length of . We can now find the perimeter of the triangle by adding up the lengths of its sides: , so the perimeter of the triangle is .

### Example Question #14 : How To Find The Perimeter Of A Triangle

What is the perimeter of a triangle with a side length of ?

Possible Answers:

Correct answer:

Explanation:

There is no certainty of the type of triangle described in this situation.  This can be an equilateral triangle, isosceles triangle, scalene triangle, or a right triangle.

There is not enough information to determine the perimeter since we only have the dimension of one side.

### Example Question #15 : How To Find The Perimeter Of A Triangle

Find the perimeter of a right isosceles triangle with a hypotenuse of .

Possible Answers:

Correct answer:

Explanation:

Write the Pythagorean Theorem.

In an isosceles triangle, the legs are equal:

Solve for the leg.

The perimeter is the sum of the legs and the hypotenuse.

### Example Question #16 : How To Find The Perimeter Of A Triangle

A triangle has the side lengths , , and .  What is the perimeter of the triangle?

Possible Answers:

Correct answer:

Explanation:

The perimeter of a triangle is the sum of the three sides.

Add the lengths together to find the perimeter.

### Example Question #17 : How To Find The Perimeter Of A Triangle

What is the PERIMETER of the triangle in the figure?

Possible Answers:

Correct answer:

Explanation:

Because the question asks you to find the PERIMETER of the triangle, you are looking to figure out the distance around the outside of the triangle. You find the perimeter of triangles simply by adding the length of the three sides together. So the correct answer here is , or .

### Example Question #18 : How To Find The Perimeter Of A Triangle

What is the PERIMETER of the triangle in the figure?

Possible Answers:

Correct answer:

Explanation:

Because the question asks you to find the PERIMETER of the triangle, you are looking to figure out the distance around the outside of the triangle. You find the perimeter of triangles simply by adding the length of the three sides together. So the correct answer here is , or .

### Example Question #19 : How To Find The Perimeter Of A Triangle

What is the PERIMETER of the triangle in the figure?

Possible Answers:

Correct answer:

Explanation:

Because the question asks you to find the PERIMETER of the triangle, you are looking to figure out the distance around the outside of the triangle. You find the perimeter of triangles simply by adding the length of the three sides together. Then the correct answer here is , or 80 cm.

### Example Question #20 : How To Find The Perimeter Of A Triangle

The perimeter of an equilateral triangle is  mm.  Which choice shows the correct side lengths?

Possible Answers:

Correct answer:

Explanation:

When finding the perimeter of any triangle, you will need to add all three sides. In this case, it is important to note that this is the perimeter of an equilateral triangle. An equilateral triangle has  congruent/equal sides. All the choices add up to  mm (except the choice that shows multiplication instead of addition), but only one choice shows  equal sides that add up to      mm: