Question

A train moves passing a man and a bridge of 260m long in 8 seconds and 10 seconds. What is the speed of the train?
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Answer 1

Solution :

In the above question, it is mentioned that the train passes a man in 8 seconds and a bridge in 10 s respectively. The length of the bridge is 260 m.

We need to find the length of the train here.

Let us assume that the length of the train is x m.

The speed of the train remains constant in both cases.

Speed While Passing Man :

> x/8 s

Speed while crossing bridge :

> (x + 260)/10

Both are equal

> x/8 = (x+260)/10

> 10x = 8(x + 260)

> 10x = 8x + 2280

> 2x = 2280

> x = 1140 m .

The train is hence 1140 m long

Speed of the train : 140 m/s.

This is the required answer,

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Answer 2

Answer:

Given :-

• Length of Bridge = 260 m
• Time(man) = 8 sec
• Time (bridge) = 10 sec

To Find :-

Speed

Solution :-

Let the speed be y

When reach to man = y/8

When reach to bridge = y + 260/10

$\sf \to \: \dfrac{y}{8} = \dfrac{y + 260}{10}$

$\dag {\mathfrak {\blue{ \underline{By \: Cross \: Multiplication}}}}$

$\sf \to \: 10 \times y =8( y + 260)$

$\sf \to \: 10y = 8y + 2280$

$\sf \to \: 10y - 8y = 2280$

$\sf \to \: 2y = 2280$

$\sf \to \: y = 1140$

Length of train = 1140 m

Speed of train = 140 m/s