You recently bough a book end whose face forms a right triangle. You want to know the length of the longest side, but you don't have a ruler. Luckily, you know that the two shorter sides are 18 inches and 24 inches. Find the length of the last side.

The problem describes a right triangle with two known sides. Finding the last side sounds like a job for Pythagorean Theorem. If you look carefully, you might see another way.

So, recall the classic:

We know a and b, and we need to find c.

So our answer is 30.

The alternate way to solve this is to see that we have a 3/4/5 Pythagorean Triple.

This means that our side lengths follow the ratio 3:4:5

We can see this by dividing our two given sides by 6.

So our scale factor is 6. This means we can get our answer by multiplying 5 and 6

So we get the same thing. Keep an eye out for Pythagorean Triples when working with right triangles in order to solve problems faster!

Start by drawing out the trapezoid in question.

Notice that triangle  is a right triangle. Thus, we can use the Pythagorean theorem to find the length of segment .

Since we know that  is also , then that means the length of segment  must also be .

Now, we can use the Pythagorean Theorem again to find the length of .

Now we can find the perimeter of the entire isosceles trapezoid.

Make sure to round to two places after the decimal.

Notice that the diagonal of the rectangle is also the diameter of the circle. We can use the Pythagorean Theorem to find the length of the diagonal.

From this, we can find the radius of the circle.

Recall how to find the area of a circle.

Plug in the given radius.

We need to use the Pythagorean Theorem to find the missing side;

The theorem says:

"For any right triangle, with legs  and  and hypotenuse , the formula  can be used to find any missing side of this triangle."

So, we are given  and  in the question...

We will plug them into the theorem:

Simplify:

Simplify:

Add:

To find , we must take the square root of both sides:

So..

Reduce:

Simplify:

For this problem, you just need to remember your handy Pythagorean theorem. Remember that it is defined as:

where  and  are the legs of the triangle, and  is the hypotenuse. Remember, however, that this only works for right triangles. Thus, based on your data, you know:

or

Subtracting 484 from each side of the equation, you get:

Using your calculator to calculate the square root, you get:

Rounding, this is , so the triangle's other leg measures .

For this problem, you just need to remember your handy Pythagorean theorem. Remember that it is defined as:

where  and  are the legs of the triangle, and  is the hypotenuse. Remember, however, that this only works for right triangles. Thus, based on your data, you know:

or

Subtracting 1056784 from each side of the equation, you get:

Using your calculator to calculate the square root, you get:

The length of the missing side of the triangle is .

The inner rectangle, which represents the garden, has length and width  feet and  feet, respectively, so its perimeter is

  feet.

The four sides of a rhombus have equal length, so we can eliminate three choices by demonstrating that at least two sidelengths are not equal.

:

1,000 meters is, by definition, equal to 1 kilometer, not 0.1 kilometers. Therefore,

and this choice is incorrect.

:

1 mile is, by definition, equal to 5,280 feet, not 1,760 feet. Therefore,

and this choice is incorrect.

By definition, 1 decimeter, not 0.1 decimeter, is equal to 1 meter. Therefore,

and this choice is incorrect.

:

 yard is equal to  inches and, also,  feet. Therefore,

All four sides have equal length so this is the rhombus. This is the correct choice.

A polygon with six sides is called a hexagon.

By definition, any polygon with four sides is called a quadrilateral. All three figures fit this description.