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by GmatKiss » Sat Oct 08, 2011 11:42 am
At a certain instant in time, the number of cars, N, traveling on a portion of a certain highway can be estimated by the formula N = (20LD)/(600+[S^2]) where L is the number of lanes in the same direction, d is the length of the portion of the highway, in feet, and s is the average speed of the cars, in miles per hour. Based on the formula, what is the estimated number of cars traveling on a
1/2 mile portion of the highway if the highway has 2 lanes in the same direction and the average speed of the cars is 40 miles per hour? (5,280 feet = 1 mile)

(A) 155
(B) 96
(C) 80
(D) 48
(E) 24
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by gmatclubmember » Sat Oct 08, 2011 11:46 am
I get the answer as D (48) after plugging in all values
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by fcabanski » Sat Oct 08, 2011 3:25 pm
At a certain instant in time, the number of cars, N, traveling on a portion of a certain highway can be estimated by the formula N = (20LD)/(600+[S^2]) where L is the number of lanes in the same direction, d is the length of the portion of the highway, in feet, and s is the average speed of the cars, in miles per hour. Based on the formula, what is the estimated number of cars traveling on a
1/2 mile portion of the highway if the highway has 2 lanes in the same direction and the average speed of the cars is 40 miles per hour? (5,280 feet = 1 mile)


20LD / 600+s^2 = 20*2*2640 / 600 + 40^2 = 48
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by parul9 » Sun Oct 09, 2011 12:54 am
The answer would be D - 48.
Directly plugging in the values in the formula would solve it.
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by ProGMAT » Tue Aug 20, 2013 9:40 am
parul9 wrote:The answer would be D - 48.
Directly plugging in the values in the formula would solve it.
Why speed is not converted into feet/hr from mile/hr (as we are using 2640 feet instead of 1/2 mile)?
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by [email protected] » Tue Aug 20, 2013 4:18 pm
Hi All,

This exact same prompt appears in the OG13 edition as well.

A similar discussion appeared in this thread:

https://www.beatthegmat.com/in-this-why- ... 66640.html

We DON'T convert miles/hour to feet/hour because the question doesn't ask us to.

GMAT assassins aren't born, they're made,
Rich
Contact Rich at [email protected]
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