In a class consisting of 40 boys and 30 girls. $30 \%$ of the boys and $40 \%$ of the girls are good at…
In a class consisting of 40 boys and 30 girls. $30 \%$ of the boys and $40 \%$ of the girls are good at Mathematics. If a student selected at random from that class is found to be a girl, then the probability that she is not good at Mathematics is
$\frac{3}{5}$
$\frac{2}{5}$
$\frac{3}{10}$
$\frac{7}{10}$
Solution
$40 \%$ of girls are good in maths
$\Rightarrow \frac{40}{100} \times 30=12$ girls are good in maths
18 girls are not good at mathematics
Required probability $=\frac{18}{30}=\frac{3}{5}$