SSC CGL 18 Aug 2021 Shift 2 Paper

Let total number of students in class is 100 .
Then, total number of boys
$=100\times \frac{45}{100}=45$
and total number of girls
$=100-45=55$
Now, Number of boys who failed
$=45\times \frac{40}{100}=18$
Number of girls who failed
$=55\times \frac{30}{100}=16.5$
Total number of students who failed
$=18+16.5=34.5$
$\therefore$ Required percentage
$=\frac{34.5}{100}\times 100=34.5\%$