Answer:
140
Explanation:
The table is:
|Sample 1 | Sample 2
catfish | 3 | 5
bass | 9 | 9
trout | 8 | 6
all fish | 20 | 20
The average number of trouts is (8 + 6)/2 = 7
The average number of the total amount of fish is 20
So, there are 7 trouts within 20 fish. To find the expected number of trouts in a population of 400 fish, we have to solve the next proportion:
7 trouts / 20 fish = x trouts / 400 fish
x = 7*400/20
x = 140 trouts