How to find the perimeter of a right triangle

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SSAT Upper Level Quantitative › How to find the perimeter of a right triangle

Questions 1 - 7
1

What is the perimeter of a right triangle with legs of length and , respectively?

Explanation

In order to find the perimeter of the right triangle, we need to first find the missing length of the hypotenuse. In order to find the hypotenuse, use the Pythagorean Theorem:

, where and are the lengths of the legs of the triangle, and is the length of the hypotenuse.

Substituting in our known values:

Now that we have the lengths of all sides of the right triangle, we can calculate the perimeter:

2

A right triangle has leg lengths of and . Find the perimeter of this triangle.

Explanation

First, use the Pythagorean Theorem to find the length of the hypotenuse.

Substituting in and for and (the lengths of the triangle's legs), we get:

Now, add up the three sides to find the perimeter:

3

What is the perimeter of a right triangle with a hypotenuse of length and a leg of length ?

Not enough information provided

Explanation

In order to find the perimeter of the right triangle, we need to first find the missing length of the second leg. In order to find the second leg, use the Pythagorean Theorem:

, where and are the lengths of the legs of the triangle, and is the length of the hypotenuse.

Substituting in our known values:

Subtracting from each side of the equation lets us isolate the variable for which we are solving:

Now that we have the lengths of all three sides of the right triangle, we can calculate the perimeter :

4

Find the perimeter of a right triangle with two legs of length and , respectively.

Not enough information provided

Explanation

In order to find the perimeter of the right triangle, we need to first find the missing length of the hypotenuse. In order to find the length of the hypotenuse, use the Pythagorean Theorem:

, where and are the lengths of the legs of the triangle, and is the length of the hypotenuse.

Substituting in our known values:

Now that we have all three sides of the right triangle, we can calculate the perimeter:

5

The lengths of the legs of a right triangle are units and units. What is the perimeter of this right triangle?

units

units

units

units

Explanation

First, we need to use the Pythagorean Theorem to find the hypotenuse of the triangle.

Now, add up all three side lengths to find the perimeter of the triangle.

6

What is the perimeter of a right triangle with hypotenuse and a leg of length ?

It cannot be determined from the information given.

Explanation

Using the Pythagorean Theorem, the length of the second leg can be determined.

We are given the length of the hypotenuse and one leg.

The perimeter of the triangle is the sum of the lengths of the sides.

7

Which of these polygons has the same perimeter as a right triangle with legs 6 feet and 8 feet?

A regular octagon with sidelength one yard.

A regular pentagon with sidelength one yard.

A regular hexagon with sidelength one yard.

None of the other responses is correct.

A regular decagon with sidelength one yard.

Explanation

A right triangle with legs 6 feet and 8 feet has hypotentuse 10 feet, as this is a right triangle that confirms to the well-known Pythagorean triple 6-8-10. The perimeter is therefore feet, or 8 yards.

We are looking for a polygon with this perimeter. Each choice is a polygon with all sides one yard long, so we want the polygon with eight sides - the regular octagon is the correct choice.

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