You catch, tag, and release 50 fish back into a pond. Then, you catch 25 more fish, 5 of which are tagged. What is the best estimate of the number of fish in the pond?

A. 100 fish

B. 250 fish

C. 400 fish

D. 625 fish

(A) 100 fish is the answer

The answer is B. 250 fish. This is a statistics problem, where the sample set taken from the pond illustrates the occurrence % of tagged fish. In finding that 5/25 fish are tagged after depositing the 50 fish, there is a 20% occurrence rate of tagged fish. (5/25 = 0.2 or 20%). This means that the 50 fish initially deposited represents only 20% of the total fish (a proportion), so 50 tagged x 5 fish (1 tagged per five) equals 250 fish total.