选择题
2014 AMC 8 Problem 25: Bike Path Semicircles
A straight one-mile stretch of highway, 40 feet wide, is closed. Robert rides his bike on a path composed of semicircles as shown. If he rides at 5 miles per hour, how many hours will it take to cover the one-mile stretch? Note: 1 mile = 5280 feet.
2014 AMC 8 第25题 ：自行车道半圆
40英尺宽的直线一英里长的高速公路被封闭。如图所示，罗伯特在由半圆组成的路径上骑自行车。如果他以每小时5英里的速度行驶，一英里路程需要多少小时？注意： 1英里= 5280英尺。
A.
π/11
B.
π/10
C.
π/5
D.
2π/5
E.
2π/3