Question

Two trains are moving with equal speed in opposite directions along two parallel railway tracks. If the wind is blowing with speed $u$ along the track so that the relative velocities of the trains with respect to the wind are in the ratio $1:2,$ then the speed of each train must be

• A. $3u$
• B. $2u$
• C. $5u$
• D. $4u$

Answer 1

Answer: (A)

$3u$

Answer 2

Let the speed of trains be v.
$\therefore$ $\frac{v-u}{v+u}=\frac{1}{2}$
or $2v-2u=v+u$
or $v=3u$