Aptitude - Time and Distance - Discussion
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Read more:"Two things are infinite: the universe and human stupidity; and I'm not sure about the universe."
- Albert Einstein
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The ratio between the speeds of two trains is 7 : 8. If the second train runs 400 kms in 4 hours, then the speed of the first train is:
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70 km/hr | [B]. |
75 km/hr | | [C]. |
84 km/hr | [D]. |
87.5 km/hr |
Answer: Option E
Explanation:
Let the speed of two trains be 7x and 8x km/hr.
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400 |
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= 100 |
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 Speed of first train = (7 x 12.5) km/hr = 87.5 km/hr.
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Asit said:
(Tue, Feb 1, 2011 07:19:07 AM)
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Let the speed of 1st train is x km/hr
2nd train speed =distance/time
So 400/4=100km/hr
now given that their ratio= 7:8(i.e 1st/2nd)
so x/100 = 7/8
=>x=87.5km/hr |
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Prajweetha said:
(Tue, May 3, 2011 05:43:57 AM)
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Second train runs at 400kms in 4 hours, so in 1 hour its speed is 400/4=100kms/hr.
Let speed of first train be "x".
Ratio is 7:8=x:100.
Then 8x=7*100.
X=700/8.
=87. 5km/hr. |
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Sandeep said:
(Sat, Aug 27, 2011 08:46:02 PM)
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Its a ration sum..
then..
Second train runs at 400kms in 4 hours, so in 1 hour its speed is 400/4=100kms/hr.
Now according to ratio concept:-
7:8
means..
total is 15..
then 8/15*x=100
we get,187.5 total speed of both the tain.
now
for first train speed..
7/15*187.5= 87.5 km/hr |
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x =