Five persons in a group of 20 are grauduate

[TomJerry]

Question:
Five persons in a group of 20 are grauduate. If 3 are picked out of 20 at random,
i) compute the probability that all are graduate
ii) find atleast one being graduate.

Solution:

i) P(all grauduate being selected) = 5C3 / 20C3 [Is this correct]

ii) P(atleast 1 being graduate) = (5C1 . 15C2 / 20C3) + (5C2 . 15C1 / 20C3) + (5C3 . 15C0 / 20C3) [Is this correct]

 

[Dickfore]

Hint: Hypergeometric Distribution.

 

[TomJerry]

Hint: Hypergeometric Distribution.

Need to know if the answer are correct or no