All Basic Geometry Resources
Example Questions
Example Question #151 : Circles
Find the area of a circle that has a diameter of 10cm.
The area formula for a circle is,
The radius is half the diameter. Since half of 10 is 5, that makes the radius 5.
Substituting the radius into the area formula results in the final answer.
Example Question #152 : Circles
Find the area of a circle whose radius is 5.
Note:
The formula for the area of a circle is
.
Plugging in the numbers,
Example Question #153 : Circles
Find the area of a circle whose radius, , is 120.
Note:
The formula for area of a circle is
.
Using the information given,
Example Question #154 : Circles
Find the area, , of a circle whose radius, , is 20.
Note:
The formula for area of a circle is
.
Using the values given, we get
Example Question #155 : Radius
The circumference of a circle is . What is its area?
The circumference of a circle is , so in this case . Dividing by 2 gives us . The area of a circle is , so in this case
Example Question #155 : Circles
True or false: a circle with radius 1 has area .
False
True
False
The area of a circle given its radius can be calculated using the formula
.
Substitute 1 for and evaluate:
Example Question #157 : Radius
What is the area of the area shaded yellow in the circle above in square miles?
The area of a circle given its radius is . The region shaded yellow in the circle given in the problem is times the area of the entire circle . Hence, this region's area can be computed as follows:
Hence, the area of the yellow region in square miles is square miles.
Example Question #158 : Radius
Circle A has radius twice that of Circle B.
True or false: The area of Circle A is four times that of Circle B.
False
True
True
The ratio of the areas of two circles is the square of the ratio of their radii. Since the ratio of the radii is , the ratio of the areas is . The given statement is true.
Example Question #151 : Plane Geometry
True or false: A circle with diameter 100 has area .
False
True
False
Given the radius of a circle, the area of the circle can be calculated using the formula
.
The radius of the circle is one half of its diameter, so here,
and, substituting for and evaluating,
.
The statement is false.
Example Question #1 : How To Find The Length Of A Radius
The area of a circle is one square yard. Give its radius in inches, to the nearest tenth of an inch.
The area of a circle is
Substitute 1 for :
This is the radius in yards. The radius in inches is 36 times this.
20.3 inches is the radius.