Question

you need 4 eggs , there are 12 eggs in the refrigerator but do not realise that 2 of these are rotten . what is the probability that none is rotten of the 4 eggs you choose at random ?

Answer 1

prob(rotten) = 2/2 = 1/6

prob(not rotten) = 5/6

You want prob that none of 4 are rotten
= C(4,0)(1/6)^0 (5/6)^4
= 1(1)(625/1296)
= 625/1296