# A goods trains 1680 metres long and travelling at the speed of 48 km per hr. leaves Jaipur at 7 am. Another mail train 5320 meters long and travelling

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A goods trains 1680 metres long and travelling at the speed of 48 km per hr. leaves Jaipur at 7 am. Another mail train 5320 meters long and travelling at the average speed of 67 km per hr. leaves Jaipur at 12 noon and follows the goods train. At what distance from Jaipur will the mail train completely cross the goods train?

1. 188 kms
2. 190 kms
3. 192 kms
4. 871 kms

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Correct Answer - Option 4 : 871 kms

Given:

Speed of goods train whose length is 1680 m and starts at 7 am = 48 km/hr

Speed of mail train whose length is 5320 m and starts at 12 noon = 67 km/hr

Concept used:

Relative speed when direction is same = Difference of both speeds

Distance = Speed × Time

Calculation:

Relative speed = (67 – 48) km/hr

⇒ 19 km/hr

Distance covered by goods train between 7 am to 12 noon (5 hours)  = (48 × 5) km

⇒ 240 km

So, Total distance = 240 km + 1680 m + 5320 m

⇒ 240 km + 7 km = 247 km

Time taken by mail train to cross goods train = 247/19

⇒ 13 hours

Distance covered by mail train in 13 hours = (13 × 67) km

⇒ 871 km

∴ The required distance is 871 km