Resistors in Parallel

This problem is intended to help you build up some intuition about resistors in parallel and should be done without a calculator. The questions below refer to the following two circuits:

If $R_1 = R_2 = 118\Omega$, for what value of $R_3$ (in Ohms) will $i_{s1} = i_{s2}$?

$R_3 =~$

If $R_1 = 136\Omega$, and $R_2 = 10K\Omega$, for approximately what value of $R_3$ (in Ohms) will $i_{s1} = i_{s2}$?

$R_3 =~$

If $R_1 = 166\Omega$, and $R_2 = 1\Omega$, for approximately what value of $R_3$ (in Ohms) will $i_{s1} = i_{s2}$?

$R_3 =~$