求大牛指点一道数学题 GWD Math2 Q6

青衿

以下这道题，GWD给的答案是B? 偶题目怎么也读不懂，请大牛指教。不胜感激！：）



Q6:











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

A.   5½ft
B.    7½ft
C.    8½ ft
D.   9½ft
E.    10ft

sdcar2010

6^2 + (x+0.5)^2 = 10^2

BBBBBBBBBBBBBBB

yiweiayumi

先问问楼主答案是哪个

青衿

不好意思，刚开始在CD发帖子，图没贴上来，图就是一个半圆，标着直径20ft。