Question

In a certain town, 40% of the people have brown hair, 25% have brown eyes and 15% have both brown hair and brown eyes. If a person selected at random from the town, has brown hair, the probability that he also has brown eyes, is

• A. $\frac { 1 } { 5 }$
• B. $\frac { 3 } { 8 }$
• C. $\frac { 1 } { 3 }$
• D. $\frac { 2 } { 3 }$

Answer 1

Answer: (B)

$\frac { 3 } { 8 }$

Answer 2

$P ( B ) = \frac { 25 } { 100 }$ and $P ( A \cap B ) = \frac { 15 } { 100 }$

So $P \left( \frac { B } { A } \right) = \frac { P ( A \cap B ) } { P ( A ) } = \frac { 15 / 100 } { 40 / 100 } = \frac { 3 } { 8 }$