All High School Math Resources
Example Questions
Example Question #61 : Circles
To the nearest tenth, give the area of a circle with diameter 17 inches.
The radius of a circle with diameter 17 inches is half that, or 8.5 inches. The area of the circle is
Example Question #92 : Plane Geometry
A circle has a radius of . A second circle has a radius of . What is the ratio of the larger circle's area to the smaller circle's area?
The area of a circle is given by the equation , where is the area and is the radius of the circle. Use this formula to determine the areas of the two circles:
and
units squared and units squared.
The ratio of the larger circle to the smaller circle is . Divide each side of the ratio by to express it in its simplest form, .
Example Question #62 : Circles
What is the area of a circle with a radius of ?
The equation for the area of a circle is .
By substituing the given radius of into the equation, we get .
Example Question #94 : Plane Geometry
As illustrated above, a square has one side that is the diameter of a circle. If the area of the square is units, what is the area of the circle?
units squared
units squared
units squared
units squared
units squared
units squared
Find the length of one side of the square by using the formula for the area of a square, , where is the length of one side, with the given information.
units
Since the side of the square forms the diameter of the circle, half of the side will be the length of the circle's radius. The radius is thus calculated as
units.
Now use this radius in the equation for the area of a circle, :
units squared
Example Question #93 : Plane Geometry
A 12x16 rectangle is inscribed in a circle. What is the area of the circle?
100π
10π
120π
50π
90π
100π
Explanation: Visualizing the rectangle inside the circle (corners touching the circumference of the circle and the center of the rectangle is the center of the circle) you will see that the rectangle can be divided into 8 congruent right triangles, with the hypotenuse as the radius of the circle. Calculating the radius you divide each side of the rectangle by two for the sides of each right triangle (giving 6 and 8). The hypotenuse (by pythagorean theorem or just knowing right triangle sets) the hypotenuse is give as 10. Area of a circle is given by πr2. 102 is 100, so 100π is the area.
Example Question #71 : Circles
A circle has a radius of 5 inches. What is the area of the circle in square inches?
The area of a circle is found by squaring the circle's radius and multiplying the result by .
Example Question #31 : Plane Geometry
A circle is inscribed in a square whose side is 6 in. What is the difference in area between the square and the circle, rounded to the nearest square inch?
The circle is inscribed in a square when it is drawn within the square so as to touch in as many places as possible. This means that the side of the square is the same as the diameter of the circle.
Let
So the approximate difference is in area
Example Question #96 : Geometry
Find the area of the shaded region:
The formula for the area of a circle is:
where is the radius of the circle.
In order to find the area of the shaded region, you must subtract the area of the inside circle from the area of the outside circle.
Therefore, the formula becomes:
Plugging in our values, we get:
Example Question #41 : Radius
Find the area of a circle with a circumference of .
The formula for the circumference of a circle is:
,
where is the radius of the circle.
To solve for the radius, plug in our existing values:
The formula for the area of a circle is:
,
where is the radius of the circle.
Plugging in our values, we get:
Example Question #46 : Radius
Find the area of the following circle:
The formula for the area of a circle is
,
where is the radius of the circle.
Plugging in our values, we get: