Question

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Answer 1

Answer:

$A=\pi \frac{d^2}{4}$

Step-by-step explanation:

The typical equation for the area of a circle is $A=\pi r^2$. Since the answer choices are in terms of d, the diameter of the circle, you will need to find r in terms of d.

To find r in terms of d, you know that the diameter of a circle is two times its radius. As an equation, this is

$d=2r$, or solving for r,

$r = \frac{d}{2}$.

Now that you have an equation for r in terms of d, you can substitute r with $\frac{d}{2}$ from the original equation.

$A=\pi r^2$

$A=\pi (\frac{d}{2})^2$

$A=\pi \frac{d^2}{4}$