Question 341016
A naturalist estimated the total number of rainbow trout in a certain lake using the capture-mark-recapture technique. 
He netted, marked, and released 200 rainbow trout.
 A week later, allowing for thorough mixing, he again netted 200 trout, and found 8 marked ones among them.
 Assuming that the proportion of marked fish in the second sample was the same
 as the proportion of all marked fish in the total population, estimate the
 number of rainbow trout in the lake.
:
Let a = actual amt of fish
:
{{{a/200}}} = {{{200/8}}}
Cross multiply
8a = 200*200
8a = 40000
a = {{{40000/8}}}
a = 5000 fish