Subject: General Aptitude · Chapter: Time and Distance · Exam: · Marks: · Difficulty:
$A$ is faster than $B . A$ and $B$ each walk 24 km. The sum of their speeds is 7 km/hr and the sum of times taken by them is 14 hours. Then, $A$ 's speed is equal to
(a)3 km/hr
(b)4 km/hr
(c)5 km/hr
(d)7 km/hr
Answer
Answer (as printed): B
Explanation
Let A's speed $=x \mathrm{km} / \mathrm{hr}$. Then, B's speed $=(7-x) \mathrm{km} / \mathrm{hr}$. So, $\frac{24}{x}+\frac{24}{(7-x)}=14 \Leftrightarrow 24(7-x)+24 x=14 x(7-x)$ $\Leftrightarrow \quad 14 x^{2}-98 x+168=0$ $\Leftrightarrow \quad x^{2}-7 x+12=0$ $\Leftrightarrow \quad(x-3)(x-4)=0$ $\Leftrightarrow \quad x=3$ or $x=4$. Since $A$ is faster than $B$, so A's speed $=4 \mathrm{km} / \mathrm{hr}$ and B's speed = 3 km/hr.