How many fishes are in the lake?

Question

To estimate the number of fishes in the lake biologist tagged 50 fishes and released him in the lake. Later they netted 108 fishes and found 27 of them that were tagged. About how many fishes are in the lake?

Answer 1

You can think this through without an equation...

 

When they netted the fishes, they found that 27/108 were tagged.  27/108 is 1/4.

 

So based on that they could estimate that 1/4 of the fish in the lake are tagged.  They tagged 50.  So 50 is 1/4 of what number? 

 

The answer is 200.

 

Or you can use an equation by looking at this as a ratio problem:

 

27 / 108 = 50 / x

 

You'd get the same answer.