at a higher speed?

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at a higher speed?

by sanju09 » Mon Mar 26, 2012 1:01 am
Train A travels from Town P to Town Q, while Train B travels from Town Q to Town P. Both trains start at the same time. Town R lies between Town P and Town Q. Which train travels at a higher speed?
(1) Train A crosses Town R earlier than Train B does.
(2) Town R lies midway between Town P and Town Q.
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by Anurag@Gurome » Mon Mar 26, 2012 2:07 am
sanju09 wrote:Train A travels from Town P to Town Q, while Train B travels from Town Q to Town P. Both trains start at the same time. Town R lies between Town P and Town Q. Which train travels at a higher speed?
(1) Train A crosses Town R earlier than Train B does.
(2) Town R lies midway between Town P and Town Q.
Speed = Distance/Time

(1) Train A crosses Town R earlier than Train B does is clearly NOT sufficient as we don't know that distance traveled

(2) Town R lies midway between Town P and Town Q is again NOT sufficient as we don't know that time taken.

Combining (1) and (2), we know that town R lies midway between town P and town Q implies that both trains traveled the same distance. Since train A crosses town R earlier than train B implies that speed of train A is more than that of train B; SUFFICIENT.

The correct answer is C.
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