Robert C. answered • 09/25/12
Tutor
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Dr. Robert can help you with Math and Science
The answer is not 2 hours.
The trains will meet up when the first train has been going for 3 hours and the second train has been going for 2.5 hours. Each will have travelled 180 miles at that point in time.
t is the time that the first train has been traveling in hours.
t-0.5 is the time that the second train has been traveling in hours.
Distance that the first train travels during that time is
t*60
Distance that the second train travels is
(t-0.5)*72
The two trains are at the same distance when those two expressions are equal
t*60 = (t-0.5)*72
60t = 72t-36
36 = 12t
3 = t
I hope that helps.
FREDERICK S.
That should help, Robert, because you laid out all the steps.
The most important thing for this student to learn is that distance - rate*time
and the units must be compatible - minutes or hours on time; distance in miles, let's say; and thus - if hours are used - rate is in miles per hour.
IF they can manage all this, there is no stopping the trains!
[I hope there are two tracks or the secod one runs into the first one!]
Good work.
10/19/12