several JJ to confirm[转帖]
38.一个相片贴在相框里，相片的长是宽的两倍，边框宽度都是2inch，
边框的面积是192平方inch，问相片长度。
[确认]：30
my solution to this question:
suppose the width of the picture is W, the I can get the equation:
(W+2)(2W+2)=192...however, I can't get the correct answer...
I am wondering whether the answer is correct or something wrong with my solution.
圆锥体侧面积=1/2*2R*pai*L=pai*R*L L:圆锥体的母线长
一道JJ提到的，母线是什么东东了？我中学都忘了。
56． y is the line between 10 and 40,
three times as many y to 10 as to 40, what is y?
a. 32, b. 32+1/3 , c. 32 +1/2, d. 33.
After calcualtion without getting an answer, I gave it up. Actually I still have 8 minutes left after I finished math. But it occurred in the middle, I don't know what other questions will be.
[确认]：C
[思路]：according to the conditions, three times as many y to 10 as to 40, we can get the relationship as following （y-10）=3(40-y). work out the equation and y=32.5 is the answer.
我怎么认为是： 3(y-10)=(40-y) ?? 关键是那句话的理解。
4. In an insurance company, each policy has a paper record and an electric record. For those policies having incorrect paper record, 60% also having incorrect electric record; For policies having incorrect electric record, 75% also having incorrect paper record. 3% of all policies have both incorrect paper and incorrect electric records. If we randomly pick out one policy,what's the probability that the one having both correct paper and correct electric records?
answer: 94%
设 pi为 incorrect paper record, ei 为 incorrect electric record, A为all policies
60%pi= 75%ei= 3%A
pi/A=1/20 ei/A=1/25 答案为：19/20* 24/25=91.2%
哪里错了？ |
