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radius and speed

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radius and speed

by 2008 » Sat Aug 09, 2008 8:23 am
A log with a radius of 2.5 feet is rolled up a hill. If it takes 30 seconds to roll the log one complete revolution, approximately how many minutes will it take to roll the log 75 yards? [3 feet = 1 yard]

A- 5
B- 7
C- 10
D- 12
E-15
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by sudhir3127 » Sat Aug 09, 2008 8:38 am
I would go with B. 7

here it goes..

Circumference of a circle is 2*pi*r ( r = 2.5)

hence its 5*pi which is approx 16 ( 5*22/7)

75 yards = 75*3 feet = 225 feet

hence its 225/ 16 = 14 revloutions of log

If each revolution takes 30 seconds, take 14 revolutions / 2 (for half a minute) = 7 minutes


hope it helps

whats the OA
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by 2008 » Sat Aug 09, 2008 8:42 am
OA is B
thanks!
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