The current in an electrical conductor varies inversely as the resistance of the conductor. what is the current when the resistance is 42 ohms, if the current is 4 amperes when the resistance is 168 ohms?

The inverse relationship between the current and the resistance can be expressed as follows, where the product of the current and the resistance is constant:



Once you establish this relationship, just plug in the numbers given:



Another way to think of this is that, in an inverse relationship, if one quantity is multiplied by a certain factor, the other quantity must be divided by that same factor, and vice versa. Since the ohms are being divided by 4:



Then the amperes must be multiplied by 4:

The correct answer is addition