A 5 ltr bucket of water is taken from a swamp. The water contains 75 mosquito larvae. A 200mL flask of water is taken from the bucket for further analysis. What is the probability that the flask contains at least one mosquito larvae?
75 larv / 5000 ml = .0015 l/ml
.0015 larv / ml x 200 ml = 3 larv should be in the sample
out of 200 l arv 3