Subject: General Aptitude · Chapter: Ratio and Proportion · Exam: 2009 · Marks: · Difficulty:
The ratio of the number of boys and girls in a school of 720 students is 7 : 5. How many more girls should be admitted to make the ratio 1 : 1?
(a)90
(b)120
(c)220
(d)240
Answer
Answer (as printed): B
Explanation
Number of boys $=\left(720 \times \frac{7}{12}\right)=420$; Number of girls $=(720-420)=300$. Let the required number of girls be $x$. Then, $\frac{420}{300+x}=1$ $$\Rightarrow 420=300+x \Rightarrow x=120 .$$
Explanation as extracted from the printed page; notation may be imperfect.