Some math questions on Dec 18(转自Robert之家)

2002-12-19 14:54:37

A few questions I can remember:
1. An insurance company has a paper record and an electronic record for every claim. For an inaccurate paper record, 60% chances that the electronic record is inaccurate. For an inaccurate electronic record, 75% chances that the paper record is inaccurate. 3% of all the claims are inaccurate both in paper record and in electronic record. Pick one claim randomly, what are the chances that it is both accurate in paper record and in electronic record?
A.97% B.94% C.68% D.65% E.35%
I chose C in the end, but not sure. This one is quite bothering.

2. On XY plane. If a line goes through Point A (A, 5), A is not equal to 5,is the slope of the line<0?
a. Line goes through (0, -2)
b. Line goes through (5, A)
I chose B,maybe it's wrong. I don't understand why people think it's D, what does the first condition tell you if you don't know what the value of A is?

3、一个多项式，X*X+B*X+16，求B？
1） X*X+B*X+16=（X+C）^2,对于所有的X，及部分C成立
2） B>0
－－－－－－－－－－－－－－－
This one bothered me before the test, it is still brothering me now. I don't quite get the choice others posted, C? For a specific value of c, there is always one specific value of b,if the equation does not hold for all c,doesn't it mean that there are some unknown value of c, in this case how do we know what's b.

4. An irregular pentagon ABCDE, AB=3,BC=2,CD=4,DE=5(I think it's 5, not 100% sure, or maybe it's 6), what are the possible values of AE? The choices are combinations of 5,10,15.

I chose 5 only.

Well, here they are. Hope it's helpful.

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