MATHEMATICS · Numerical · AoPS · Mathematics · Ratios and Percents · Ratios and Percents
Problem
A lake contains 250 trout, along with a variety of other fish. A marine biologist catches and releases a sample of 180 fish from the lake, of which 30 are trout. Assume that the ratio of trout to the total number of fish is the same in both the sample and the lake. How many fish are there in the lake?