To determine the number of trout in a lake, conservationist catches 161 trout, tags them and throuws them back into the lake. Later, 39 trout are caught: 13 of them are tagged. How many trout would the conservationist expect to be in the lake?

Answer 1

from the 13 tagged out of the 39 caught ...
13/39 = 1/3

so (1/3)x = 161
x = 483

Answer 2

Two hundred trout were tagged and then released into a pond. Later 60 trout were caught and examined, and 8 of the 60 trout were found to have tags. Estimate the number of trout in the pond.