Question

A biologist catches 21 fish in a lake and tags and releases them. In the same lake a few days later, 50 fish are caught with 7 having tags. How many fish are in the lake?

Answer 1

set up a proportion
21 tagged fish / total number = 7 tagged / 50
if we call N the total number, solve for N in
\[ \frac{21}{N}= \frac{7}{50} \]
can you do that ?

Answer 2

yes i can