Henry know that the circumference of a circle is 18 pie inches. What is the area of the circle?

A:36

B:81

C:162

D:324

B: 81π inches

Step-by-step explanation:

The formula for the circumference of a circle is C = πd and the formula for the area of a circle is A = πr²

The formula for the circumference of a circle can also be written as C = 2πr since the diameter is equal to double the radius (d = 2r) So we need to solve for r since that is the variable we are missing in order to solve for the area

Plugging in our known values to the circumference formula we have:

18π = 2πr Then dividing both sides by 2π we have 9 = r

Now that we have solved for the radius, we can plug in this value to the area formula:

A = π (9) ² = 81π in