An ecologist catches 25 fish tags them and releases them back in the pond. She catches 30 fish on the next day, of which 10 carry the tag. Assuming that the fish in the pond remain unchanged and each fish has equal probability of being caught, what is the estimated number of fish in the pond?

Correct option is B

Given:
· First catch: 25 fish tagged.
· Second catch: 30 fish.
· Tagged fish in the second catch: 10.
· We need to estimate the total number of fish in the pond (N).
Concept: The proportion of tagged fish in the second catch is equal to the proportion of tagged fish in the total population:
(Tagged fish in second catch) / (Total fish in second catch) = (Tagged fish in the population) / (Total fish in the population)
This gives us:
10 / 30 = 25 / N
Solution: Rearranging the equation to find N:
N = (25 × 30) / 10
N = 75
Answer: The estimated number of fish in the pond is 75.
Correct Option: (b) 75