Question

Wind is blowing west to east along two parallel tracks. Two trains moving with same speed in opposite directions have the relative velocity with respect to wind in the ratio $1:2$. The speed of each train is

• A. equal to that of wind
• B. double that of wind
• C. three times that of wind
• D. half that of wind

Answer 1

Answer: (C)

three times that of wind

Let $v$ be velocity of wind and $u$ be velocity of each train.
Relative velocity of one train with respect to wind $=2\times$ Relative velocity of other train with respect to wind
$u+v=2(u-v)$
$v+2v=2u-u=u$
i.e., $u=3v$.