SOLUTION: The Metro Rail travels 240 km at a uniform rate.If the speed had been 8 km per hour more,the journey would have taken 1 hour less.what is the speed of the train?

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Question 162015: The Metro Rail travels 240 km at a uniform rate.If the speed had been 8 km per hour more,the journey would have taken 1 hour less.what is the speed of the train?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
d+=+r%2At
Given:
d+=+240km
If the speed was r+%2B+8 km/hr
the time would have been t+-+1hr
The equations are:
240+=+r%2At and
240+=+%28r+%2B+8%29%2A%28t+-+1%29
240+=+rt+%2B+8t+-+r+-+8
And, since 240+=+r%2At,
240+=+240+%2B+8t+-+r+-+8
Subtract 240 from both sides
0+=+8t+-+r+-+8
r+=+8%2A%28t+-+1%29
Substitute this in 240+=+r%2At
240+=+8%2A%28t+-+1%29%2At
240+=+8t%5E2+-+8t
Divide both sides by 8
t%5E2+-+t+-+30+=+0
%28t+-+6%29%28t+%2B+5%29+=+0
t+=+-5
t+=+6 hrs
240+=+r%2At
r+=+240+%2F+t
r+=+240%2F6
r+=+40 km/hr
The speed of the train was 40 km/hr
check answer:
240+=+r%2At
240+=+%28r+%2B+8%29%2A%28t+-+1%29
240+=+%2840+%2B+8%29%2A%286+-+1%29
240+=+48%2A5
240+=+240
OK