Ben is driving on the highway at x miles per hour ( one miles equals 5280 feet) Ben's tires 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
Ben
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HI J_shreyans,
This question is perfect for TESTing VALUES, but once you get to a certain point in your work, you won't have to check every answer  you should be able to recognize a pattern and save some time.
We have a car driving at X miles per hour that has tires with a CIRCUMFERENCE of Y feet each. The fact that the variable is for the circumference actually saves us a number of "math steps." Here's why.
Let's TEST....
X = 2
Y = 3
The car is traveling 2 miles per hour, which means it travels 2(5280) feet per hour. If you'd like to calculate that, then that's fine, but it's not really necessary. Each tire has a circumference of 3 feet, meaning that for each complete revolution/rotation, the tire has moved 3 feet.
So, the car traveled 2(5280) feet and each rotation is 3 feet. This gives us....
2(5280)/3
Visually, this means that the "X" is in the numerator and the "Y" is in the denominator. The correct answer is the only one that fits that pattern.
Final Answer: A
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Rich
This question is perfect for TESTing VALUES, but once you get to a certain point in your work, you won't have to check every answer  you should be able to recognize a pattern and save some time.
We have a car driving at X miles per hour that has tires with a CIRCUMFERENCE of Y feet each. The fact that the variable is for the circumference actually saves us a number of "math steps." Here's why.
Let's TEST....
X = 2
Y = 3
The car is traveling 2 miles per hour, which means it travels 2(5280) feet per hour. If you'd like to calculate that, then that's fine, but it's not really necessary. Each tire has a circumference of 3 feet, meaning that for each complete revolution/rotation, the tire has moved 3 feet.
So, the car traveled 2(5280) feet and each rotation is 3 feet. This gives us....
2(5280)/3
Visually, this means that the "X" is in the numerator and the "Y" is in the denominator. The correct answer is the only one that fits that pattern.
Final Answer: A
GMAT assassins aren't born, they're made,
Rich
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Let y = 10560 feet.j_shreyans wrote:Ben is driving on the highway at x miles per hour ( one miles equals 5280 feet) Ben's tires 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
Since 10560 feet = 2 miles, the circumference of each tire = 2 miles.
Let x = 2 miles per hour.
Since Ben is traveling at 2 miles per hour, and the circumference of each tire = 2 miles, the number of revolutions per hour = 1. This is our target.
Now plug x=2 and y=10560 into the answers to see which yields our target of 1.
Only A works:
5280(x/y) = 5280(2/10560) = 1.
The correct answer is A.
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Here's an algebraic approach:j_shreyans wrote:Ben is driving on the highway at x miles per hour ( one miles equals 5280 feet) Ben's tires 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
Each tire has a circumference of y feet.
So, there will be 1 revolution every time the car travels y feet.
5280/y = the number of times y divides into 5280.
So, if the car travels 5280 feet (aka 1 mile) in one hour, then there will be 5280/y revolutions.
If the car travels (x)(5280) feet (aka x miles) in one hour, then there will be (x)(5280/y) revolutions.
(x)(5280/y) = 5280x/y = [spoiler]5280(x/y)[/spoiler]
Answer: A
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We are given that Ben is driving at an average rate of x mph and we need to determine how many revolutions each wheel turns in one hour.j_shreyans wrote:Ben is driving on the highway at x miles per hour ( one miles equals 5280 feet) Ben's tires 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
Since 1 mile = 5,280 feet, Ben drives 5280x feet in one hour.
Thus, the number of revolutions is distance/circumference = (5,280x)/y = 5280(x/y).
Answer: A
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