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Two trains are traveling on a collision course...

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by BTGmoderatorLU » Sat Jan 20, 2018 8:00 am
Two trains are traveling on a collision course. If train A is traveling at a speed of 350mph 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

The OA is A.

I'm really confused with this PS question. Experts, any suggestion?

If train B is traveling 28% slower than train A, then speed of train B should be 252mph and the initial distance between the two is 1505 miles...

Time before collision will be, total distance / total speed, I know the total distance, but how can I get the total speed?

Thanks in advance.
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by [email protected] » Sat Jan 20, 2018 1:04 pm
Hi LUANDATO,

We're told that two trains are traveling on a collision course - Train A is traveling at a speed of 350 mph and Train B is traveling 28% slower. We're asked how much time it will take the trains to collide if the initial distance between the two is 1505 miles. Since the trains are traveling towards each other, this is a Combined Rate question.

To start, we can calculate the speed of Train B:

1% of 350 = 3.5 so...
28% of 350 = (28)(3.5) = 98

Thus, Train B is traveling 350 - 98 = 252 mph

This means that the TOTAL distance traveled by the 2 trains EACH hour = 350 + 252 = 602 miles. We know that the distance between the trains is 1505 miles, so we can use the Distance Formula to solve for the time it takes the trains to meet:

Distance = (Rate)(Time)
1505 miles = (602 mph)(Time)
1505/602 = T
T = 2.5 hours

Final Answer: A

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by Jeff@TargetTestPrep » Fri Jan 26, 2018 12:30 pm
LUANDATO wrote:Two trains are traveling on a collision course. If train A is traveling at a speed of 350mph 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

Answer: A

Jeffrey Miller
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