Question

A train passes two bridges of lengths $800$ m and $400$ m in $100$ seconds and $60$ seconds respectively. The length of the train is

• A. $80$ m
• B. $90$ m
• C. $200$ m
• D. $150$ m

Answer 1

The correct option is C $200$ m

Let the length of first train be $x$ m and speed of train be $x$ knph.

Speed $s=\frac{x+800}{100}$ ....(1)

Speed $s=\frac{x+400}{60}$ ....(2)

Equating equations (1) and (2), we get

$\frac{x+800}{100}=\frac{x+400}{60}$

$\Rightarrow 5x+2000=3x+2400$

$\Rightarrow 2x=400$

$\Rightarrow x=200$

Therefore, the length of train is $200$ m.