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and a second wheel

by sanju09 » Fri Jul 23, 2010 6:10 am
A wheel has a diameter of x inches and a second wheel has a diameter of y inches. The first wheel covers a distance of d feet in 100 revolutions. How many revolutions does the second wheel make in covering d feet?
A. 100xy
B. 100y - x
C. 100x - y
D. 100y / x
E. 100x / y

[spoiler]Source: majortests.com[/spoiler]
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by kvcpk » Fri Jul 23, 2010 6:20 am
A wheel has a diameter of x inches and a second wheel has a diameter of y inches. The first wheel covers a distance of d feet in 100 revolutions. How many revolutions does the second wheel make in covering d feet?

Diameter is x
Hence perimeter = pi * x

for Second wheel pi*y

(pi*x)*100 = d

(pi*y)*number = d
(pi*y)*number = (pi*x)*100
number = 100x/y

pick E
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by blaster » Fri Jul 23, 2010 6:29 am
kvcpk wrote:A wheel has a diameter of x inches and a second wheel has a diameter of y inches. The first wheel covers a distance of d feet in 100 revolutions. How many revolutions does the second wheel make in covering d feet?

Diameter is x
Hence perimeter = pi * x

for Second wheel pi*y

(pi*x)*100 = d

(pi*y)*number = d
(pi*y)*number = (pi*x)*100
number = 100x/y

pick E
good explanation!
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by kvcpk » Fri Jul 23, 2010 6:34 am
blaster wrote:
kvcpk wrote:A wheel has a diameter of x inches and a second wheel has a diameter of y inches. The first wheel covers a distance of d feet in 100 revolutions. How many revolutions does the second wheel make in covering d feet?

Diameter is x
Hence perimeter = pi * x

for Second wheel pi*y

(pi*x)*100 = d

(pi*y)*number = d
(pi*y)*number = (pi*x)*100
number = 100x/y

pick E
good explanation!
Thanks Blaster :)
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by selango » Fri Jul 23, 2010 6:36 am
Distance=Number of revolutions*diameter

D=100*x

D=N*y

100*x=N*y

N=100x/y

Pick E
--Anand--
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by beastly B » Tue Dec 28, 2010 5:21 pm
blaster wrote:
kvcpk wrote:A wheel has a diameter of x inches and a second wheel has a diameter of y inches. The first wheel covers a distance of d feet in 100 revolutions. How many revolutions does the second wheel make in covering d feet?

Diameter is x
Hence perimeter = pi * x

for Second wheel pi*y

(pi*x)*100 = d

(pi*y)*number = d
(pi*y)*number = (pi*x)*100
number = 100x/y

pick E
good explanation!
thanks it helped blaster:D
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by Taran » Thu Feb 03, 2011 10:16 pm
I solved it by picking numbers
First Wheel: Let x (dia) = 12 inches => Radius of first wheel = 6 inches
Circumference of first wheel = 2 Pi r = 2 Pi 6 = 12 Pi inches or Pi feet

Second Wheel: let y (dia) = 6 inches => Radius = 3 inches
Circumference of second wheel = 2 Pi r = 2 Pi 3 = 6 Pi inches or Pi/2 feet

Now, first wheel covers Pi feet in one revolution, so will cover 100 Pi feet in 100 revolutions (i.e d = 100 Pi feet)
Second Wheel covers Pi/2 feet in 1 revolution or covers 1 feet in 2/Pi revolutions. Thus it will cover d = 100 Pi feet in 100 Pi x 2/Pi revolutions. Solve it to get 200 revolutions.

Now your answers, when plugged with x = 12 and y = 6, should yield 200. Only E does that, hence is correct answer.
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by maddy2u » Wed Feb 23, 2011 12:50 pm
answer is E
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by Bharadwaj Charan » Wed Mar 09, 2011 8:26 pm
Distance traveled by first wheel is 100pi*x, the second wheel travels the same distance

so 100*pi*x/pi*y (which is the perimeter) --> so it is 100*x/y(pi cancels pi)

E is the answer. :)

this is my first post on Beat the GMAT... :D
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by sanju09 » Thu Mar 10, 2011 12:23 am
Bharadwaj Charan wrote:Distance traveled by first wheel is 100pi*x, the second wheel travels the same distance

so 100*pi*x/pi*y (which is the perimeter) --> so it is 100*x/y(pi cancels pi)

E is the answer. :)

this is my first post on Beat the GMAT... :D
your most welcome, Bharadwaj Charan, and E is the right answer, hence congratulations too :)
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by sushantgupta » Mon Jul 04, 2011 12:14 pm
answer is E
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by wingsoffire » Sun Oct 09, 2011 8:09 am
its an E . nice sum i SAY !
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by parul9 » Sun Oct 09, 2011 8:16 am
E - 100x/y!
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by Abhishek009 » Sun Oct 09, 2011 9:08 am
sanju09 wrote:A wheel has a diameter of x inches and a second wheel has a diameter of y inches. The first wheel covers a distance of d feet in 100 revolutions. How many revolutions does the second wheel make in covering d feet?
A. 100xy
B. 100y - x
C. 100x - y
D. 100y / x
E. 100x / y

[spoiler]Source: majortests.com[/spoiler]
Radius of the first wheel is x/2

So circumference of the wheel ( distance covered in one rotation ) = 2 * pi * ( x/2)

So in 100 revolutions it covers

2 *pi * ( x ) *100 = d





Now , the radius of the second wheel will be y / 2

So distance covered in 1 rotation will be

2* pi * y/2



Turns made by this wheel be " t " { Say }


So distance covered is :


2 * pi * y/2 * t

Now the same distance is covered by both ....


2 *pi * y/2 *t = 2 * pi * x/2 *100


y * t = 100 x

So t = 100 x / y



Option E.
Abhishek
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by ronnie1985 » Thu Mar 29, 2012 10:46 am
100x/y QED
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