Question

The ratio between the speeds of two trains is $7:8.$ If the second train runs $400km$ in $4$ hours, then the speed of the first train is:

• A. $70kmph$
• B. $75kmph$
• C. $84kmph$
• D. $87.5kmph$

Answer 1

The correct option is D $87.5kmph$

Let the speed of two trains be $7x$ and $8x$ km/hr.

It is given that the second train runs $400$ km in $4$ hours, therefore, we have:

$8x=\frac{400}{4}$

$\Rightarrow 8x=100$

$\Rightarrow x=\frac{100}{8}$

$\Rightarrow x=12.5$

Hence, the speed of the first train is $7\times 12.5=87.5$ kmph.