A pair of numbers is picked up randomly (without replacement) from the set {1,2,3,5,7,11,12,13,17,19}. The probability that the number 11 was picked given that the sum of the numbers was even is nearly `0. 1` b. `0. 125` c. `0. 24` d. `0. 18`

Answer

C

Explanation

Let A be the evetn that 11 is picked and B be the event that sum is even. The number of ways of selecting 11 along with one more odd number is n `(AnnB)=""^(7)C_(1).`
The number of ways of selecting either two even numbers or selecting two odd numbers is `n(B)=1+""^(8)C_(2).`
`P(A//B)=(P(AnnB))/(P(B))=7/29=0.24`