Biologists use direct variation to estimate the number of individuals of a species i...

Biologists use direct variation to estimate the number of individuals of a species in a particular area. They first capture a sample of individuals from the area and mark each specimen with a harmless tag. Later, they return and capture another sample from the same area. They base their estimate on the theory that the proportion of tagged specimens in the new sample is the same as the proportion of tagged individuals in the entire area. Use this idea to work Exercises 51 and 52.

Estimating Fish in a Lake Biologists tagged 250 fish in City Park Lake on October 12. On a later date, they found 7 tagged fish in a sample of 350. Estimate, to the nearest hundred, the total number of fish in the lake