Solve 4/pi*A=4pi*r*d

$$\frac { 4 } { \pi } \cdot A = 4 \pi \cdot r \cdot d$$

Solve for A

$$A=\pi ^{2}dr$$

Steps for Solving Linear Equation

The equation is in standard form.

$$\frac{4}{\pi }A=4\pi dr$$

Divide both sides by 4\pi ^{-1}.

$$\frac{\frac{4}{\pi }A\pi }{4}=\frac{4\pi dr\pi }{4}$$

Dividing by 4\pi ^{-1} undoes the multiplication by 4\pi ^{-1}.

$$A=\frac{4\pi dr\pi }{4}$$

Divide 4\pi rd by 4\pi ^{-1}.

$$A=\pi ^{2}dr$$

Solve for d

$$\left\{\begin{matrix}d=\frac{A}{\pi ^{2}r}\text{, }&r\neq 0\\d\in \mathrm{R}\text{, }&A=0\text{ and }r=0\end{matrix}\right.$$

Steps for Solving Linear Equation

Express \frac{4}{\pi }A as a single fraction.

$$\frac{4A}{\pi }=4\pi rd$$

Swap sides so that all variable terms are on the left hand side.

$$4\pi rd=\frac{4A}{\pi }$$

Divide both sides by 4\pi r.

$$\frac{4\pi rd}{4\pi r}=\frac{4A}{\pi \times 4\pi r}$$

Dividing by 4\pi r undoes the multiplication by 4\pi r.

$$d=\frac{4A}{\pi \times 4\pi r}$$

Divide \frac{4A}{\pi } by 4\pi r.

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