[求助]GMAT Pre 中的几道数学题

如果图像不清楚，烦请点击打开，就会清楚了

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3)没懂题

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4)答案C，偶做的是A）81

恳请指教。bow～～～

http://forum.chasedream.com/dispbbs.asp?boardID=22&ID=163195&page=1

did you search here first?

Yes, I did. I've search it twice and on your recommendation,I search it for the third round just now and get some answer (How careless I was during the first two rounds) Thanks for your advice.

I post the answer here for the one who have the same questions as me and faild to find them.

1)http://forum.chasedream.com/dispbbs.asp?boardid=22&id=155675&star=1#1460596(by hitlzc)

A是喜欢的概率：0.3

B是喜欢的概率0.7*0.3＝0.21

C是喜欢的概率0.7*0.7*0.3＝0.147

总和0.657

2)Didn't get it

3)http://forum.chasedream.com/dispbbs.asp?boardID=22&ID=162178&page=1(by hitlzc)

某种仪表可以测0-10伏的电压（包括0和10），如果3次记录的平均值是8，问最小可能电压是多少？

那就使得另两次最大，取10伏，所以最小可能电压＝8*3-10-10＝4

(看来阅读真是很重要噢。根本就没读明白：）

4)http://forum.chasedream.com/dispbbs.asp?boardid=22&replyid=1428785&id=150134&page=1&skin=0&Star=1（by Mko)

"the tricky thing is the answers were given like this: (81), (27), ... instead of 81, 27....so when 81 comes out as the result, and since it's an odd, it has to be set back to (m) = 3m, therefore, the answer is (27) = 81, answer is (27), answer 81 is correct, however, it's not available in any of the answers...81 is not (81)."

Could anybody help me on the third one?

Thanks in advance

2.INTERNET:80+10=90

X:90*90%(1+10%)=89.1

Y:90

Z:90*(1+10%)-10=89

 the third one 有什么问题？能详细说明下吗？

Got it，i made a mistake on rebate .

many thanks