An express train traveled at an average speed of 100 kilometers per hour, stopping for 3 minutes after every 75 kilometers. A local train traveled at an average speed of 50 kilometers, stopping for 1 minute after every 25 kilometers. If the trains began traveling at the same time, how many kilometers did the local train travel in the time it took the express train to travel 600 kilometers?
A)300
B)305
C)307.5
D)1200
E)1236
Friday, December 28, 2007
QUESTION#15
Posted by Gaurav & Kunal at 10:53 PM
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1 Comment:
According to me, the answer is C) 307.5
First of all, we should find the time taken by the Express train for 600 km.
Now, it takes 3 min break after each 75 km.
For, the 600 km, it's avg speed being 100, it takes 6 hrs.
The break time is 3 min after first 75 + 3 min after 150 + ... 3 min after 525km
i.e. break time is 21 min. (The last 3 min shud not be taken because 600 km are over)
Now, in 6 hr and 21 min, the local train has to run.
Now, local train runs at avg speed of 50 kmph and it stops 1 min after each 25 km,
so we can consider it takes 1 hr and 2 min to cover each 50 km.
Thus, in 6 hr and 12 min, it will cover 300 km.
In the left 9 min, it will cover, 50 * 9 / 60 i.e. 7.5 km (because no break in last 9 minutes)
Thus, it will cover 307.5 km
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