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Two trains for Mumbai leave Delhi at 6 am and 6.45 am and travel at 10

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Bunuel
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Two trains for Mumbai leave Delhi at 6 am and 6.45 am and travel at 10 [#permalink] New post   20 Mar 2016, 09:48
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Two trains for Mumbai leave Delhi at 6 am and 6.45 am and travel at 100 kmph and 136 kmph respectively. How many kilometers from Delhi will the two trains be together.

A. 260 km
B. 262.4 km
C. 275 km
D. 283.33 km
E. 300 km
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D
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Re: Two trains for Mumbai leave Delhi at 6 am and 6.45 am and travel at 10 [#permalink] New post   20 Mar 2016, 10:42
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In the first 45 minutes, train A is able to travel 100 kmh * (3/4) h = 75 km.
The relative speed of the second train to the first train is 36 kmh. Thus we need to find the time that the second train will take to cover that distance:
D = s*t
75 = 36kmh * t ==> t = 75/36 h

Now we need to find the distance traveled in that amount of time:
D = s*t
D = 136kmh * (75/36)h
D = 283.33 km

Answer: D
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Re: Two trains for Mumbai leave Delhi at 6 am and 6.45 am and travel at 10 [#permalink] New post   27 Aug 2018, 11:04
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I know this is probably a stupid objection to say. But according to me, we cannot tell when they will be together if at all. What if in 45 mins, train A has already reached Mumbai. We don't know the distance between Delhi and Mumbai do we?
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Re: Two trains for Mumbai leave Delhi at 6 am and 6.45 am and travel at 10 [#permalink] New post   04 Sep 2018, 10:14
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At 6:45 the first train already pass 100*45/60 km = 75 km
After 6:45 both trains spent equal time (t hours) until they meet.

So we have 75+100t = 136t
75 = 36t
t=75/36 hours

So total distance = 136* 75/36 = 283,33 km
Answer D

P.S. The distance between Delhi and Mumbai about 1,400 km ;)
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Re: Two trains for Mumbai leave Delhi at 6 am and 6.45 am and travel at 10 [#permalink] New post   04 Sep 2018, 10:26
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Bunuel wrote:
Two trains for Mumbai leave Delhi at 6 am and 6.45 am and travel at 100 kmph and 136 kmph respectively. How many kilometers from Delhi will the two trains be together.

A. 260 km
B. 262.4 km
C. 275 km
D. 283.33 km
E. None of these


Distance gained by first train started at 6 am till 6:45 am = 100*(45/60) = 75 km

Relative speed = 136-100=36

Time = relative distance / relative speed = 75/36 hours

distance travelled by first train = 75 +(75/36)*100 = 283.33 km

Answer: Option D
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Re: Two trains for Mumbai leave Delhi at 6 am and 6.45 am and travel at 10 [#permalink] New post   04 Sep 2018, 10:27
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mitrakaushi wrote:
I know this is probably a stupid objection to say. But according to me, we cannot tell when they will be together if at all. What if in 45 mins, train A has already reached Mumbai. We don't know the distance between Delhi and Mumbai do we?



this is a well raised objection and question should be rephrased to avoid this ambiguity. :thumbup:
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Re: Two trains for Mumbai leave Delhi at 6 am and 6.45 am and travel at 10 [#permalink] New post   03 Jul 2023, 21:42
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Re: Two trains for Mumbai leave Delhi at 6 am and 6.45 am and travel at 10 [#permalink]
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