Question

The ratio of the number of boys and girls in a college is $7:8$. If the percentage increase in the number of boys and girls be $20\%$ and $10\%$ respectively, what will be the new ratio?

• A. $8:9$
• B. $17:18$
• C. $21:22$
• D. Cannot be determined

Answer 1

The correct option is C $21:22$

Originally, let the number of boys and girls in the college be $7x$ and $8x$ respectively.

The percentage increase in the number of boys and girls is $20\%$ and $10\%$ respectively,

Their increased number is ($120\%$ of $7x$) and ($110\%$ of $8x$).

$(\frac{120}{100}\times 7x)$ and $(\frac{110}{100}\times 8x)$

=> $\frac{42x}{5}$ and $\frac{44x}{5}$

$\therefore$ The required ratio = $(\frac{42x}{5}:\frac{44x}{5})$ $=21:22$