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标题: 请教！这道题是什么意思？ [打印本页]

作者: dearsue 时间: 2009-12-7 10:58
标题: 请教！这道题是什么意思？

The figureabove shows the dimensions of a semicircular cross section of a one-waytunnel. The single traffic lane is 12feet wide and is equidistant from the sides of the tunnel. If vehicles must clear the top of the tunnelby at least ½ foot when they are inside the traffic lane, what should be thelimit 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

作者: zliycdr 时间: 2009-12-7 11:09
标题: 我想选D。。。
虽然题目么看懂，不过感觉20/2-1/2~

作者: allennuli 时间: 2009-12-7 11:42
LZ想象一下一辆12feet宽的汽车要通过隧道所能取的最大高度，再把这个高度减去1/2foot就行了

作者: a10285 时间: 2009-12-7 13:33
同意ls，半圆形隧道直径20，则铁轨12且与两边距离相等（4），要求vehicle至少与隧道顶部距1/2
如vehicle与隧道顶部接触，根据勾股定理，根号(10^2-6^2)=8，8-1/2= 7½ ft 选B.

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