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#36095

equations

algebra

hard

120 sec

The formula for the total resistance $R_{T}$ of two resistors $R_{1}$ and $R_{2}$ connected in parallel is given by $\frac{1}{R _{T}} = \frac{1}{R _{1}} + \frac{1}{R _{2}}$ . If $R_{1} = 3 R_{2}$ , which expression is equivalent to $R_{T}$ in terms of $R_{2}$ ?

A.

$\frac{4}{3} R_{2}$

B.

$\frac{3}{4} R_{2}$

C.

$4 R_{2}$

D.

$\frac{1}{4 R _{2}}$