Expected number

[rahul goyal]

4 bad apples accidentally got mixed up with 20 good apples.
In a draw of 2 apples at random, expected number of bad apples is
(a) 1
(b) 2/3
(c) 1/3
(d)1/6

[kvcpk]

4 bad apples accidentally got mixed up with 20 good apples.
In a draw of 2 apples at random, expected number of bad apples is
(a) 1
(b) 2/3
(c) 1/3
(d)1/6

Probability of picking the bad apple in first pick = 4/24 = 1/6
Probability of picking bad apple in nth pick is same the first pick. Hence in second pick also 1/6

Hence total probability = 1/6 + 1/6 = 1/3

Hope this helps!!