Discussion Forum



1)

If a die is rolled  twice and the sum of the numbers appearing on them is observed to be 6 , then the probability that the number 1 appears atleast once on them is 


A) $\frac{5}{36}$

B) $\frac{2}{5}$

C) $\frac{11}{36}$

D) $\frac{1}{3}$

Answer:

Option B

Explanation:

Consider the events

A= sum of the number appearing on them is 6.

B= Number 1 appears atlleast once

 P(A)= $\frac{5}{36}$  , P(B)= $\frac{11}{36}$

 $P(A\cap B)=\frac{2}{36}$

$\therefore$  Required  probability P(B/A)=  $\frac{P(A\cap B)}{P(A)}=\frac{2/36}{5/36}=\frac{2}{5}$