Question

A and B run around a circular track of length 600 m at a speed of 15 m/s and 12 m/s respectively. They start at the
same time from the same point in opposite direction. When will they meet for the first time at the starting
point?
(a) 100 sec
(b) 200 sec
(C) 60 sec
(d) 2 hr
(e) None of the

Answer 1

$d=t\times s$ ($d$, $t$, and $s$ means distance, time and speed.)

Because they start in opposite direction,

the sum of their distance should be $600k$ m($k$ is an natural number.).

The minimum of the sum is 600 m.

$d_A=t_A\times 12$ ($d_A$ and $t_A$ means distance and time of A)

$d_B=t_B\times 15$ ($d_B$ and $t_B$ means distance and time of B)

But $t_A=t_B$.

Let $t_A=t_B=T$.

Then, $d_A+d_B=600$ and $d_A+d_B=27T$.

∴ $T=\frac{200}{9}$

They will meet after $\frac{200}{9}$ second.

The answer is (e) None of the above.