prep2-178、140

附图：

[attachimg]70522[/attachimg]

178.
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[?]

In the figure shown, point O is the center of the semicircle and points B, C, and D lie on the semicircle.  If the length of line segment AB is equal to the length of line segment OC, what is the degree measure of angle BAO ?

(1)  The degree measure of angle COD is 60.

(2)  The degree measure of angle BCO is 40.

答案是D，请大家帮忙看看为什么，谢谢。

附图：

[attachimg]70523[/attachimg]

140.
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A manufacturer produced x percent more video cameras in 1994 than in 1993 and y percent more video cameras in 1995 than in 1994.  If the manufacturer produced 1,000 video cameras in 1993, how many video cameras did the manufacturer produce in 1995 ?

[1] xy=20

[2] x+y+xy/100=9.2

答案是B，我算的是如果x+y+xy=9.2就没问题，但是除100就算不出来了，请指点一下，谢谢。

第一题里面

C=2A，因为边都是相等的，是两个等腰三角形。所以都可以算出来。

第二道题，你列下式子：1000*（1+x%）*（1+y%)=10*(x+y+xy%),注意乘的时候%不要忘记了。

178估计lz和我一样纠结1）

还是贴张图看着方便

由图可得x+y+60=180=2x+2x+y

可推出x=20,y可销去

[attachimg]70529[/attachimg]

178估计lz和我一样纠结在1）

见图，由图可推x+y+60=180=2x+2x+y

y可销去，可推出x=20