In an aquarium, there are 10 large fish and 5 small fish. Half of the large fish are red.
One fish is selected at random. Find the probability that it is a large, red fish.
Write your answer as a fraction in simplest form.
The probability of selecting a large fish is 10/(10+5)=10/15.
The probability of selecting a red fish given that it is large is 1/2.
Therefore, the probability of selecting a large, red fish is (10/15)*(1/2)=(10/30)=1/3. Answer: \boxed{\frac{1}{3}}.