OG16 PS 84题

琳二

OG16. P213
84.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=200Ld/(600+s²)
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.98
C.80
D.48
E.24


看了OG的解释，仍然搞不懂，为什么不把mile和feet化为同一个单位？就是直接把所有数值带进去吗？求大神解释！！！！

leoman

题写错了那是20， 题说二分之一 mile,所以 5280 乘以0.5， 剩下带公式， 最后得48

无为

只需要把D 换算成feet
S平方 题目中没说要从mph换成feet per hour 假如需要换算 这题估计没有计算器 算不出 common sense就是不需要换的
LZ题目公式也写错了

琳二

leoman 发表于 2016-1-5 21:07
题写错了那是20， 题说二分之一 mile,所以 5280 乘以0.5， 剩下带公式， 最后得48 ...

我开始怀疑我智商了，还是没有理解到啊。。题写错了吗？

琳二

求解答！！！