MCQ
The average marks of boys in class is $52$ and that of girls is $42.$ The average marks ofboys and girls combined is $50.$ The percentage of boys in the class is
- ✓$80$
- B$60$
- C$40$
- D$20$
$\therefore 52 x+42 y=50(x+y)$
$52 x+42 y=50 x+50 y$
$52 x-50 x=50 y-42 y$
$2 x=8 y$
$x=4 y$
Total number of students in the class $=x+y$
$=4 y+y$
$=5 y$
Percentage of boys $=\frac{4 y}{5 y} \times 100^{20}$
$=80$
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
| Class: | $0-10$ | $10-20$ | $20-30$ | $30-40$ | $40-50$ |
| Frequency | $2$ | $3$ | $x$ | $5$ | $4$ |
is $28$ , then its variance is $........$.