Subject: General Aptitude · Chapter: Ratio and Proportion · Exam: 2008 · Marks: · Difficulty:
In a school the ratio of boys and girls is 4 : 5 respectively. When 100 girls leave the school the ratio becomes 6 : 7 respectively. How many boys are there in the school?
(a)1300
(b)1500
(c)1600
(d)Cannot be determined
(e)None of these
Answer
Answer (as printed): E
Explanation
Let the number of boys and girls be $4 x$ and $5 x$ respectively. Then, $\frac{4 x}{5 x-100}=\frac{6}{7} \Rightarrow 28 x=30 x-600$ $$\Rightarrow 2 x=600 \Rightarrow x=300 .$$ ∴ Number of boys $=4 \times 300=1200$.
Explanation as extracted from the printed page; notation may be imperfect.