The first arithmetic topic that will be dealt with here is Time and Distance along with Unitary method.
Later principles of BODMAS will be taken up.
Another important topic that will be looked into is Time and Work.

Thursday, March 28, 2013

Time and Distance - 2

In what time will a train, 125 m long, moving at a speed of 45 kilometres per hour, cross a bridge 265 metres long ?

Solution: To cross a bridge, a train has to travel a distance equal to the sum of its own length and the length of the bridge. So here the train will have to travel (125 m + 265 m) = 390 m.

Now, the speed of the train is 45 Km per hour.
That is, the train covers 45 Km in 1 hour (= 60 minutes).

1 Km = 1000 metres

So, the train covers (45 x 1000) metres in 60 minutes.

therefore, the train covers 1 metre in 60 / (45 x 1000) minutes.

So the train covers 390 metres in 60 x 390 / (45 x 1000) = 52 /100 minutes.

1 minute = 60 seconds.

By multiplying minutes by 60 we gets seconds.
So 52/100 minutes = 52 x 60 / 100 seconds = 312/ 10 seconds = 31.2 seconds.

Answer: The train crosses the bridge in 31.2 seconds.

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