In a certain pond, 50 fish were caught, tagged, and returned to the pond. A few days later, 50 fish were caught again, of which 5 were found to have been tagged. If the percent of tagged fish in the second catch approximates the percent of tagged fish in the pond, what is the approximate number of fish in the pond? Choices
A) 400
B) 500
C) 1,250
D) 2,500
E) 10,000

Rationale: "total fish = x percentage of second catch = ( 5 / 50 ) * 100 = 10 % so , x * 10 % = 50 x = 500 ans b ."
Answer: B