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In a hostel, $60 \%$ of the students read Hindi newspaper, $40 \%$ read English newspaper and $20 \%$ read both Hindi and English newspapers. A student is selected at random
(a) Find the probability that she reads neither Hindi nor English newspapers.
(b) If she reads Hindi newspaper, find the probabililty that she reads english newspapers.
(c) If she reads English newspaper, find the probability that she reads Hindi newspaper.
(a) Find the probability that she reads neither Hindi nor English newspapers.
(b) If she reads Hindi newspaper, find the probabililty that she reads english newspapers.
(c) If she reads English newspaper, find the probability that she reads Hindi newspaper.
Solution:
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Verified Answer
(a) Let $\mathrm{H}$ and $\mathrm{E}$ represent the event that a student reads
Hindi and English newspaper respectively $\mathrm{P}(\mathrm{H})=0.6, \mathrm{P}(\mathrm{E})=0.4, \mathrm{P}(\mathrm{H} \cap \mathrm{E})=0.2$
Probability that the student reads at least one paper $=\mathrm{P}(\mathrm{H} \cup \mathrm{E})$
Now $\mathrm{P}(\mathrm{H})=0 \cdot 6, \mathrm{P}(\mathrm{E})=0 \cdot 4, \mathrm{P}(\mathrm{H} \cap \mathrm{E})=0 \cdot 2$
$\therefore \quad \mathrm{P}(\mathrm{H} \cup \mathrm{E})=0 \cdot 6+0 \cdot 4-0 \cdot 2=1-0.2=0.8$
$\therefore$ Probability that a student reads neither Hindi nor English newspaper
$=1-\mathrm{P}(\mathrm{H} \cup \mathrm{E})=1-0 \cdot 8=0 \cdot 2$
(b) The probability that the student reads English newspaper if she reads Hindi
$$
=\mathrm{P}(\mathrm{E} / \mathrm{H})=\frac{\mathrm{P}(\mathrm{E} \cap \mathrm{H})}{\mathrm{P}(\mathrm{H})}
$$
Now $\mathrm{P}(\mathrm{E} \cap \mathrm{H})=0 \cdot 2, \mathrm{P}(\mathrm{H})=0 \cdot 6$
$$
\therefore \mathrm{P}(\mathrm{E} / \mathrm{H})=\frac{0 \cdot 2}{0 \cdot 6}=\frac{1}{3}
$$
(c) The probability that she reads Hindi newspaper if she reads English newspaper
$$
\begin{aligned}
&=\mathrm{P}(\mathrm{H} / \mathrm{E})=\mathrm{P}(\mathrm{H} \cap \mathrm{E})=0 \cdot 2, \mathrm{P}(\mathrm{E})=0.4 \\
&\therefore \mathrm{P}(\mathrm{H} / \mathrm{E})=\frac{\mathrm{P}(\mathrm{H} \cap \mathrm{E})}{\mathrm{P}(\mathrm{E})}=\frac{0 \cdot 2}{0 \cdot 4}=\frac{1}{2}
\end{aligned}
$$
Hindi and English newspaper respectively $\mathrm{P}(\mathrm{H})=0.6, \mathrm{P}(\mathrm{E})=0.4, \mathrm{P}(\mathrm{H} \cap \mathrm{E})=0.2$
Probability that the student reads at least one paper $=\mathrm{P}(\mathrm{H} \cup \mathrm{E})$
Now $\mathrm{P}(\mathrm{H})=0 \cdot 6, \mathrm{P}(\mathrm{E})=0 \cdot 4, \mathrm{P}(\mathrm{H} \cap \mathrm{E})=0 \cdot 2$
$\therefore \quad \mathrm{P}(\mathrm{H} \cup \mathrm{E})=0 \cdot 6+0 \cdot 4-0 \cdot 2=1-0.2=0.8$
$\therefore$ Probability that a student reads neither Hindi nor English newspaper
$=1-\mathrm{P}(\mathrm{H} \cup \mathrm{E})=1-0 \cdot 8=0 \cdot 2$
(b) The probability that the student reads English newspaper if she reads Hindi
$$
=\mathrm{P}(\mathrm{E} / \mathrm{H})=\frac{\mathrm{P}(\mathrm{E} \cap \mathrm{H})}{\mathrm{P}(\mathrm{H})}
$$
Now $\mathrm{P}(\mathrm{E} \cap \mathrm{H})=0 \cdot 2, \mathrm{P}(\mathrm{H})=0 \cdot 6$
$$
\therefore \mathrm{P}(\mathrm{E} / \mathrm{H})=\frac{0 \cdot 2}{0 \cdot 6}=\frac{1}{3}
$$
(c) The probability that she reads Hindi newspaper if she reads English newspaper
$$
\begin{aligned}
&=\mathrm{P}(\mathrm{H} / \mathrm{E})=\mathrm{P}(\mathrm{H} \cap \mathrm{E})=0 \cdot 2, \mathrm{P}(\mathrm{E})=0.4 \\
&\therefore \mathrm{P}(\mathrm{H} / \mathrm{E})=\frac{\mathrm{P}(\mathrm{H} \cap \mathrm{E})}{\mathrm{P}(\mathrm{E})}=\frac{0 \cdot 2}{0 \cdot 4}=\frac{1}{2}
\end{aligned}
$$
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