Question 13·Easy·Area and Volume
A circle has a diameter of 14 centimeters. What is the area, in square centimeters, of the circle? Express your answer in terms of .
For circle problems, first check whether you are given radius or diameter. If you are given the diameter, immediately divide by 2 to get the radius. For area, always use (radius squared) and be careful not to mix this up with circumference formulas or . When a problem says "in terms of ", leave in your final answer instead of approximating it as 3.14.
Hints
Diameter vs. radius
The formula for the area of a circle uses the radius, not the diameter. How can you find the radius if the diameter is 14?
Recall the correct formula
For area of a circle, use . Make sure you are not using the formula for circumference.
Square the radius
Once you know the radius, plug it into . Be careful to square the radius before multiplying by .
Desmos Guide
Enter the area expression
In the Desmos calculator, type pi*(14/2)^2 to represent with radius .
Interpret the result
Look at the exact (symbolic) output. You should see multiplied by a whole number; that product is the circle's area in square centimeters.
Step-by-step Explanation
Convert diameter to radius
The problem gives the diameter of the circle as 14 centimeters.
The radius is half the diameter:
Recall the area formula for a circle
The formula for the area of a circle in terms of its radius is
Now we will substitute into this formula.
Substitute and simplify to find the area
Substitute into and simplify:
So, the area of the circle is square centimeters, which corresponds to choice C.