At a certain instant in time, the number of cars, \(N,\) traveling on a portion of a certain highway can be estimated by

[Vincen]

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

\(N=\dfrac{20Ld}{600+s^2}\)

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 \(\frac12\)-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

Answer: D

Source: Official Guide

[Scott@TargetTestPrep]

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

\(N=\dfrac{20Ld}{600+s^2}\)

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 \(\frac12\)-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

Answer: D

Source: Official Guide

Solution:

Substituting 2 for L, 40 for s and 2640 for d (since ½ mile = 2640 feet), we have:

N = (20 x 2 x 2640) / (600 + 40^2)

N = 105,600/2200 = 48

Answer: D