Question

find the total resistance in the diagram below.

Answer 1

R2+R3=
1/10 + 1/15 = 35/150( 1/Req)
total resistance = 30 + 150/35
= approx 35 ohm

Answer 2

For parallel resistance,
$\frac{1}{r } = \frac{1}{r1} + \frac{1}{r2} \\ \frac{1}{r} = \frac{1}{10} + \frac{1}{15} \\ \frac{1}{r} = \frac{(3 + 2)}{30} \\ \frac{1}{r} = \frac{5}{30} \\ r = 6$
Total Resistance = R1 + R2
= (30 + 6) ohms
= 36 ohms