Subject: General Aptitude · Chapter: Ratio and Proportion · Exam: · Marks: · Difficulty:
The ratio of number of boys to that of girls in a group becomes 2 : 1 when 15 girls leave. But, afterwards, when 45 boys also leave, the ratio becomes 1 : 5. Originally the number of girls in the group was
(a)20
(b)30
(c)40
(d)50
Answer
Answer (as printed): C
Explanation
Let the number of boys and girls, after leaving of 15 girls, be $2 x$ and $x$ respectively. Then, $\frac{2 x-45}{x}=\frac{1}{5} \Rightarrow 10 x-225=x$ $$\Rightarrow 9 x=225 \Rightarrow x=25 .$$ ∴ Original number of girls $=x+15=(25+15)=40$.
Explanation as extracted from the printed page; notation may be imperfect.