Suppose you have a box of identical resistors. Each resistor in the box has a resistance of 20 Ohms. Explain how to connect them together so the total resistance of the network is 25 Ohms. Use the minimum number of resistors in your design.

By using 4 resistors in parallel and followed by a resistor in series.

Explanation:

Let consider 5 resistors with a resistance of 20 ohms each, the total resistance is equal to 25 ohms when the first four resistance are settled in parallel and is followed by a resistor is series. The calculations are presented below:

1st Stage (4 resistors in parallel)

If , then:

2nd Stage (1 resistor in series)

Now, the equivalent resistance is:

i think it would be 5