Subject: General Aptitude · Chapter: Ratio and Proportion · Exam: · Marks: · Difficulty:
The least whole number which when subtracted from both the numerator and the denominator of the fractional number 6 : 7, gives a ratio less than 16 : 21, is
(a)2
(b)3
(c)4
(d)6
Answer
Answer (as printed): B
Explanation
Let the required number be $x$. Then, $\frac{6-x}{7-x}<\frac{16}{21} \Rightarrow 21(6-x)<16(7-x)$ $$\begin{aligned} & \Rightarrow 126-21 x<112-16 x \\ & \Rightarrow 5 x>14 \Rightarrow x>\frac{14}{5} \Rightarrow x>2 \frac{4}{5} \Rightarrow x=3 . \end{aligned}$$
Explanation as extracted from the printed page; notation may be imperfect.