Subject: General Aptitude · Chapter: Ratio and Proportion · Exam: 2010 · Marks: · Difficulty:
When 30\% of one number is subtracted from another number, the second number reduces to its four-fifths. What is the ratio of the first to the second number?
(a)2 : 5
(b)3 : 2
(c)4 : 7
(d)Cannot be determined
(e)None of these
Answer
Answer (as printed): E
Explanation
Let the numbers be $x$ and $y$. Then, $y-30 \%$ of $x=\frac{4}{5} y \Rightarrow y-\frac{4}{5} y=\frac{30}{100} x \Rightarrow \frac{y}{5}=\frac{3 x}{10}$ $$\Rightarrow \frac{x}{y}=\frac{1}{5} \times \frac{10}{3}=\frac{2}{3} \Rightarrow x: y=2: 3 .$$
Explanation as extracted from the printed page; notation may be imperfect.