Solve for r. $$I = \frac { E } { R + r }$$
A) $r = E - R$
B) $r = \frac { I E - R } { I }$
C) $r = \frac { E - I R } { I }$
D) $r = \frac { R - I E } { I }$

Question

Quizplus · Accepted Answer

To solve for $r$, first multiply both sides by $R + r$ to get rid of the denominator, resulting in $I(R + r) = E$. Then distribute $I$ to get $IR + Ir = E$. Subtract $IR$ from both sides to isolate $Ir$ on one side, giving $Ir = E - IR$. Finally, divide both sides by $I$ to solve for $r$, resulting in $r = \frac{E - IR}{I}$.

Solve for R I=ER+rI = \frac { E } { R + r }I=R+rE​

Solve for R $I = \frac { E } { R + r }$