this has to do with inverse variation

Question

the power in an electric circuit varies inversely with resistance. If the power is 1200 watts when the resistance is 30 ohms, find the resistance when the power is 2400 watts.

Answer 1

inverse variation is in the form

 

xy = k

 

1200(30) = 2400(x)          divide both sides by 2400

0.5(30) = x

15 = x

 

Without the algebra, as one value doubles the other value must halve.