求解一道数学（GWD2_Q6）

兔兔cx

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?



A.5½ ft

B.7½ ft

C.8 ½ ft

D.9½ ft

E.10 ft
PS:图是一个半圆，直径为20ft

annapolocko

还是不懂~ 能再讲details一点吗？？

sjhksakk

当火车的切面长方形正好与隧道的切面内切时，此时的火车高度最高为8，但是题目说If vehicles must clear the top of the tunnel by at least ½ foot when they are inside the traffic lane。。。是不是就是说火车的高度必须留下1/2的高度空间。。。
所以就是7又1/2了
个人理解，仅供参考

兔兔cx

题目是什么意思啊，真没看懂~~为什么会有三条边呢？求大神能给详细解答吗？

juventuser

B
三边6,8,10
8-0.5=7.5