All High School Math Resources
Example Questions
Example Question #31 : Circles
Consider a circle centered at the origin with a circumference of . What is the x value when y = 3? Round your answer to the hundreths place.
5.77
10.00
5.8
None of the available answers
5.778
5.77
The formula for circumference of a circle is , so we can solve for r:
We now know that the hypotenuse of the right triangle's length is 13.5. We can form a right triangle from the unit circle that fits the Pythagorean theorem as such:
Or, in this case:
Example Question #241 : High School Math
What is the radius of a circle with a circumference of ?
To find the radius of a circle given the circumference we must first know the equation for the circumference of a circle which is
Then we plug in the circumference into the equation yielding
We then divide each side by giving us
The answer is .
Example Question #2 : How To Find The Length Of A Radius
A circle has an area of 36π inches. What is the radius of the circle, in inches?
18
6
36
9
6
We know that the formula for the area of a circle is πr2. Therefore, we must set 36π equal to this formula to solve for the radius of the circle.
36π = πr2
36 = r2
6 = r
Example Question #3 : How To Find The Length Of A Radius
Circle X is divided into 3 sections: A, B, and C. The 3 sections are equal in area. If the area of section C is 12π, what is the radius of the circle?
Circle X
7
4
6
√12
6
Find the total area of the circle, then use the area formula to find the radius.
Area of section A = section B = section C
Area of circle X = A + B + C = 12π+ 12π + 12π = 36π
Area of circle = where r is the radius of the circle
36π = πr2
36 = r2
√36 = r
6 = r
Example Question #4 : How To Find The Length Of A Radius
The specifications of an official NBA basketball are that it must be 29.5 inches in circumference and weigh 22 ounces. What is the approximate radius of the basketball?
5.43 inches
9.39 inches
14.75 inches
4.70 inches
3.06 inches
4.70 inches
To Find your answer, we would use the formula: C=2πr. We are given that C = 29.5. Thus we can plug in to get [29.5]=2πr and then multiply 2π to get 29.5=(6.28)r. Lastly, we divide both sides by 6.28 to get 4.70=r. (The information given of 22 ounces is useless)
Example Question #2 : How To Find The Length Of A Radius
If the circumference of a circle is , what is the radius?
The formula for circumference is .
Plug in our given information.
Divide both sides by .
Example Question #61 : Radius
Find the radius of a circle with area .
Since the formula for the area of a triangle is
plug in the given area and isolate for . This yields 13.
Example Question #11 : How To Find The Length Of A Radius
The circumference of a circle is 45 inches. The circle's radius is ____ inches.
When you know the circumference of a circle, you can determine its diameter by dividing the circumference by . Then, when you have the diameter, you can determine the radius by dividing the diameter by 2.
Example Question #111 : Circles
A circle with center (8, –5) is tangent to the y-axis in the standard (x,y) coordinate plane. What is the radius of this circle?
5
4
16
8
8
For the circle to be tangent to the y-axis, it must have its outer edge on the axis. The center is 8 units from the edge.
Example Question #1 : Radius
A circle has an area of . What is the radius of the circle, in inches?
49 inches
7 inches
16 inches
24.5 inches
14 inches
7 inches
We know that the formula for the area of a circle is πr2. Therefore, we must set 49π equal to this formula to solve for the radius of the circle.
49π = πr2
49 = r2
7 = r