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DS Speed-Time

by prachi18oct » Tue Jul 21, 2015 1:54 pm
Ian's car has four tires each with a radius of 7 inches. How many rotations will one tire make as it travels from his school to his house?

(1) The trip takes 25% less time at 30 miles per hour than at 25 miles per hour.
(2) The route Ian takes is uphill for .7 miles and therefore that portion takes more time to travel.
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by GMATGuruNY » Tue Jul 21, 2015 2:27 pm
prachi18oct wrote:The trip takes 25% less time at 30 miles per hour than at 25 miles per hour.
(faster rate)/(slower rate) = (30 mph)/(25 mph) = 6/5.
Since rate and time are RECIPROCALS, 6/5 the rate implies 5/6 the time.
Thus, the trip at 30mph must take 1/6 LESS TIME than the trip at 25mph -- contradicting statement 1's contention that the trip takes 25% less time.

I would ignore this problem.
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by prachi18oct » Tue Jul 21, 2015 4:24 pm
GMATGuruNY wrote:
prachi18oct wrote:The trip takes 25% less time at 30 miles per hour than at 25 miles per hour.
(faster rate)/(slower rate) = (30 mph)/(25 mph) = 6/5.
Since rate and time are RECIPROCALS, 6/5 the rate implies 5/6 the time.
Thus, the trip at 30mph must take 1/6 LESS TIME than the trip at 25mph -- contradicting statement 1's contention that the trip takes 25% less time.

I would ignore this problem.
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It is from bellcurves question bank.
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by nikhilgmat31 » Wed Jul 22, 2015 4:09 am
Please check the question statement again.
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