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Tricky problem

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Tricky problem

by sparkle6 » Mon Sep 26, 2011 8:39 am
Ben is driving on the highway at x miles per hour. (One mile equals 5,280 feet). Ben's tired have a circumference of y feet. Which of the following expressions gives the number of revolutions each wheel turns in one hour?

a. 5280(x/y)
b. 5280(y/x)
c. 5280(xy)
d. 5280/xy
e. xy/5280


[spoiler]Answer: C. Please help[/spoiler]
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by aplavakarthik » Mon Sep 26, 2011 9:00 am
5280/y gives u the number of revolutions the tire make per mile.

multiplied by x gives u the total no of revolutions done per hour.

(5280/y)*x

IMO A
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by gmatclubmember » Mon Sep 26, 2011 9:08 am
sparkle6 wrote:Ben is driving on the highway at x miles per hour. (One mile equals 5,280 feet). Ben's tired have a circumference of y feet. Which of the following expressions gives the number of revolutions each wheel turns in one hour?

a. 5280(x/y)
b. 5280(y/x)
c. 5280(xy)
d. 5280/xy
e. xy/5280


[spoiler]Answer: C. Please help[/spoiler]
I dont think answer can be C.
Look at the units of the answer 5280x is the distance traveled in one hour which is in feets and y too is in feets. When we multiply those we get answer in feet squared.
Besides the correct answer is A.
Total distance covered/distance covered in one turn = 5280x(ft)/y(ft/turn) = 5280x(turn)/y
Note that the feets got cancelled and we get only the no. of turns :)

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by hitmoss » Mon Sep 26, 2011 9:24 am
{5280 x miles per hour (x)} / circumference of tire. = (5280*x)/y

Answer is A.
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by sparkle6 » Mon Sep 26, 2011 9:34 pm
Ya, I got A as well but then thought I was missing something. I guess the answer is incorrect. Thanks guys!
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by mcdesty » Sat Jul 12, 2014 1:12 pm
Here is what my scratch paper looked like when I solved this one.
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by phanikpk » Sat Jul 12, 2014 9:50 pm
Got A only.....
Thanks guys......
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by GMATinsight » Sat Jul 12, 2014 11:53 pm
Ben is driving on the highway at x miles per hour. (One mile equals 5,280 feet). Ben's tired have a circumference of y feet. Which of the following expressions gives the number of revolutions each wheel turns in one hour?

a. 5280(x/y)
b. 5280(y/x)
c. 5280(xy)
d. 5280/xy
e. xy/5280
Speed = Distance / Time

Distance Traveled by Ben in 1 hour = x miles = 5280x Feet [Given 1 mile = 5280 Feet]

Total revolution of wheel = Distance Traveled / Distance traveled in 1 revolution

[because distance traveled in 1 revolution of wheel = circumference of wheel]

Therefore, Total revolution of wheel = 5280x / y

Answer: Option A
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by [email protected] » Sun Jul 13, 2014 7:46 am
Hi All,

This question can be solved by TESTing VALUES.

We're told the speed is X miles per hour and the circumference of the tires is Y feet. The question asks how many revolutions each wheel will turn in 1 hour.

Let's keep the values small so the math will be easy:

X = 2
Y = 4

Now the speed is 2 miles per hour, so that's 2(5280 feet) per hour. I'm not going to do that math just yet though....

Since the circumference of the tires is 4 feet, we can figure out the number of revolutions by dividing the distance by 4...

2(5280)/4 = 5280/2 = 2640

When you plug in the above values for X and Y, only one answer matches 2640...

Final Answer: A

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