Question

Two indentical resistors of 20 ohm each are connected in parallel . This combination, in turn, is connected to a 10ohm resistor . The equivalent resistance of the combination will be ....

Answer 1

Equivalent Resistance in Parallel=
$\frac{a \times b}{a + b} \\ = \frac{20 \times 20}{20 + 20} \\ = \frac{400}{40} \\ = 10$
This is connected to another 10 Ohm Resistor in Series, So net Resistance
$= 10 + 10 = 20 \: ohm$