Under certain conditions of artificial light, the exposure time required to photograph an object varies directly as the candlepower of the light and varies inversely as the square of the object’s distance from the light source. If the exposure time is 0.01 second when the light source is 6.00 feet from the object, how far from he object should the light source be when both the candlepower and the exposure time are doubled?

Question

Under certain conditions of artificial light, the exposure time required to photograph an object varies directly as the candlepower of the light and varies inversely as the square of the object’s distance from the light source.  If the exposure time is 0.01 second when the light source is 6.00 feet from the object, how far from he object should the light source be when both the candlepower and the exposure time are doubled?