As part of a conservation effort for a lake,

Question

40 fish were caught, tagged and released.  Later, 80 fish were caught from the lake.  4 of these 80 were found to have tags.  Estimate the number of fish in the lake 

Answer 1

The assumption is the fraction of fish that were caught and found tagged to the fish caught is the same for the entire fish population in the lake.

 

 

We can solve the problem by forming a proportion:

 

4/80 = 40/x

 

Solve for x to find the estimated number of fish in the lake.