All Common Core: 7th Grade Math Resources
Example Questions
Example Question #26 : Area Of A Circle
What is the area of the circle provided?
In order to solve this problem, we need to recall the formula for the area of a circle:
The circle in this question provides us with the diameter, so we first have to solve for the radius. Remember, the radius is half the diameter:
Now that we have the radius we can use the formula to solve:
Solve:
Example Question #1 : Circumference Of A Circle
What is the circumference of a circle with a radius equal to ?
The circumference can be solved using the following equation:
Example Question #1 : Circumference Of A Circle
The radius of a circle is . Give the circumference of the circle in terms of .
The circumference can be calculated as , where is the radius of the circle.
Example Question #2 : Circumference Of A Circle
What is the circumference of a circle with a radius of ?
The circumference can be solved using the following equation:
Where represents the radius. Therefore, when we substitute our radius in we get:
Example Question #2 : Circumference Of A Circle
If this circle has a diameter of 12 inches, what is its circumference?
none of these
Know that the formula for circumference is , where C is the circumference and D is the diameter. It is given that the diameter is 12 inches. Therefore, the circumference is
Example Question #1 : Circumference Of A Circle
If a circle has an area of , what is the circumference of the circle?
The formula for the area of a circle is πr2. For this particular circle, the area is 81π, so 81π = πr2. Divide both sides by π and we are left with r2=81. Take the square root of both sides to find r=9. The formula for the circumference of the circle is 2πr = 2π(9) = 18π. The correct answer is 18π.
Example Question #2 : Circumference Of A Circle
If a circle has an area of , what is the circumference?
For a circle, the formula for area is and the formula for circumference is , where is the radius and is the diameter.
Plug the known quantities into the area formula and solve for the radius:
Now plug this value into the circumference formula to solve:
Example Question #4 : Circumference Of A Circle
Find the circumference of a circle with a radius of .
Recall the formula for finding the circumference of a circle:
We can substitute in the value for the radius in order to find the circumference of the circle in question.
Solve.
Simplify.
Example Question #4 : Circumference Of A Circle
Find the circumference of a circle that has a radius of .
Recall the formula for finding the circumference of a circle:
We can substitute in the value for the radius in order to find the circumference of the circle in question.
Solve.
Simplify.
Example Question #5 : Circumference Of A Circle
Find the circumference of the circle with a radius of .
Recall the formula for finding the circumference of a circle:
We can substitute in the value for the radius in order to find the circumference of the circle in question.
Solve.
Simplify.