Question

Let A and B are two events such that P(A') = 0.3, P(2) = 0.4

and P(A Ç B') = 0.5, then $P \left( \frac { B } { A \cup B ^ { \prime } } \right)$ =

• A. $\frac { 1 } { 2 }$
• B. $\frac { 3 } { 4 }$
• C. $\frac { 1 } { 4 }$
• D. $\frac { 3 } { 7 }$

Answer 1

Answer: (C)

$\frac { 1 } { 4 }$

Answer 2

P(1) = 7/10, P(2) = 4/10, P(A Ç B')

= P(1) – P(A Ç B) = $\frac { 5 } { 10 }$\ P(A Ç B) = $\frac { 2 } { 10 }$ and P(A È B')

= 1 – [P(2) – P(A Ç B)] = 1 – $\frac { 2 } { 10 }$ = $\frac { 8 } { 10 }$

Now $\frac { 2 / 10 } { 8 / 10 }$ = $\frac { 1 } { 4 }$