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# Two trains are traveling on a collision course. If train A is travelin

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Math Expert
Joined: 02 Sep 2009
Posts: 58427
Two trains are traveling on a collision course. If train A is travelin  [#permalink]

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30 Jun 2016, 07:45
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Difficulty:

65% (hard)

Question Stats:

62% (02:17) correct 38% (02:10) wrong based on 151 sessions

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Two trains are traveling on a collision course. If train A is traveling at a speed of 350 mph and train B is traveling 28% slower, how much time will it take the trains to collide if the initial distance between the two is 1505 miles?

A. Two hours and 30 minutes.
B. One hour and 10 minutes.
C. Two hours and 25 minutes.
D. Three hours and 15 minutes.
E. Four hours and 20 minutes.

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Re: Two trains are traveling on a collision course. If train A is travelin  [#permalink]

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30 Jun 2016, 09:12
1
Answer is A. Two hours and 30 minutes.

Since they are racing towards each other, the speed is accumulative, ie. 350 mph + 350*0.72 = 602 (0.72 because the second train is 28% slower)

So time before collision is total distance / total speed = 1505/602 = 2.5 hours or 2 hours and 30 mins
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Two trains are traveling on a collision course. If train A is travelin  [#permalink]

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Updated on: 30 Jun 2016, 10:23
let S1 and S2 be the speeds of train A and B
S1 is 350 and S2=28% less = 252
time taken = S1+S2/1505
which is
1505/602 =x
where 2<x<3
therefore C !!

Originally posted by CounterSniper on 30 Jun 2016, 10:08.
Last edited by CounterSniper on 30 Jun 2016, 10:23, edited 1 time in total.
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Re: Two trains are traveling on a collision course. If train A is travelin  [#permalink]

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30 Jun 2016, 10:21
Bunuel wrote:
Two trains are traveling on a collision course. If train A is traveling at a speed of 350 mph and train B is traveling 28% slower, how much time will it take the trains to collide if the initial distance between the two is 1505 miles?

A. Two hours and 30 minutes.
B. One hour and 10 minutes.
C. Two hours and 25 minutes.
D. Three hours and 15 minutes.
E. Four hours and 20 minutes.

Speed of second train= 350*72/100= 252

Time= Total distance/ total speed
1505/ 350+252

1505/602= 2.____

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Re: Two trains are traveling on a collision course. If train A is travelin  [#permalink]

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12 Jul 2016, 01:15
Hi Bunuel , I came up with option C = 1505 /602 . This is tough calculation and I used approximation and came up with little less than 2.5 hours which seems incorrect. How would you solve this?
Thanks
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Re: Two trains are traveling on a collision course. If train A is travelin  [#permalink]

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12 Jul 2016, 02:55
rakaisraka wrote:
Hi Bunuel , I came up with option C = 1505 /602 . This is tough calculation and I used approximation and came up with little less than 2.5 hours which seems incorrect. How would you solve this?
Thanks

You did everything correct but notice that 2.5 hours = 2 hours and 30 minutes. BTW 1505/602 = 2.5 exactly.
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Re: Two trains are traveling on a collision course. If train A is travelin  [#permalink]

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26 Jan 2018, 10:50
Bunuel wrote:
Two trains are traveling on a collision course. If train A is traveling at a speed of 350 mph and train B is traveling 28% slower, how much time will it take the trains to collide if the initial distance between the two is 1505 miles?

A. Two hours and 30 minutes.
B. One hour and 10 minutes.
C. Two hours and 25 minutes.
D. Three hours and 15 minutes.
E. Four hours and 20 minutes.

Since train A is traveling at a rate of 350 mph, train B is traveling at a rate of 0.72 x 350 = 252 mph.

If we let t = the time for both trains until they meet, we can create the equation:

350t + 252t = 1505

602t = 1505

t = 2.5 hours

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Re: Two trains are traveling on a collision course. If train A is travelin  [#permalink]

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06 Jul 2019, 08:24
Bunuel May I ask, why answers choices not arranged in ascending order?
Re: Two trains are traveling on a collision course. If train A is travelin   [#permalink] 06 Jul 2019, 08:24
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