有没有会这道题， 我看不懂题目的意思

ivydorian

1--------------------------1
             20ft

The figure above shows the dimensions of a semicircular cross section of a one-way tunnel.  The single traffic lane is 12 feet wide and is equidistant from the sides of the tunnel.  If vehicles must clear the top of the tunnel by at least ½ foot when they are inside the traffic lane, what should be the limit on the height of vehicles that are allowed to use the tunnel?

5½ ft
7½ ft
8 ½ ft
9½ ft
10 ft

sdcar2010

Hehe.  The car is not a single slim LINE, but a 12 feet wide block. What the question wants you to do is to draw a right angle triangle: whose horizontal side is 6, vertical side is (height + 0.5) and the longest side is 10.  6^2 +(height +0.5)^2 = 10^2

height = 7.5

bllian

我的理解是，图上的20ft是这个半圆形通道的直径（也就是半径是10feet），而通道中有一条宽为12feet的车道并且这条车道与隧道两边等距，然后可以用勾股定理算出交通工具正好碰到隧道的高度是8feet，然后题目里说在车辆行驶时至少要离隧道1/2foot，所以应该拿8-1/2=7½ ft

ivydorian

谢谢两位