Question

If a cepheid variable in a nearby galaxy is 106 times fainter than an identical one in the Milky Way, how far away is it?

Answer 1

`10.3` times as far as the one in the Milky Way.

Explanation:

Since radiation (light) gets weaker with the square of the distance, the relative distance goes up with the square root of the relative brightness going down:

`B~1/d^2->d~1/sqrtB`