[問題] GWD2-GMAT-Q6

[saikang]

有個半圓形的圖, 圓的直徑 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 tunnel by at least 1/2 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) 5 1/2 ft
(b) 7 1/2 ft
(c) 8 1/2 ft
(d) 9 1/2 ft
(e) 10 ft

答案是 b, 腦幹了半天怎麼想也想不出跟 7 1/2 有啥關係, 請解惑... :-$

[homaru]

here
http://www.formosamba.com/phpBB3/viewtopic.php?t=1732