10月数学JJ讨论（301-400）

wisdomcorn

Agree with you!Should be E.

wisdomcorn

325. DS: there are 60 items in a big, some are red objects and some are triangular objects, someone randomly pick things out of the bag, what is the probability he will pick a red object or a triangular object

1)there are 6 red objects and 8 triangular objects in the bag

2) there are three red triangular objects in the bag

I chose C, not sure tho!

Somebody plz tell me how solve such questions! thanks!

CUTEWANWAN

傻傻的问一句: 我11月21号考,应该看什么时候的jj?

NKspielberg

以下是引用juneff在2008-10-24 23:01:00的发言：

can you show me how you did it? THANK YOU

f(x)=f[(x-1)+1]=f[-(x-1)]，因此f(x+1)=f(-x)

NKspielberg

以下是引用CUTEWANWAN在2008-10-25 8:50:00的发言：
傻傻的问一句: 我11月21号考,应该看什么时候的jj?

看11月7号以后的。不用着急

NKspielberg

315.   直线k和m，
   K :y=3x+2，
   k上的点（a,b）对应m上的（b,a），问m的表达式

这道题不是DS题吧？

NKspielberg

323. DS: n is positive integer, what is the remainder of n/13

1) the remainder of n^2/13 is 10  - Insufficient

2)13<n<26

I chose C

该选E

NKspielberg

326. PS: the area of a circle is x, and the circle is inscribed in a square with parameter X. X equals to?

64/pai

How?

NKspielberg

以下是引用wisdomcorn在2008-10-25 5:14:00的发言：

325. DS: there are 60 items in a big, some are red objects and some are triangular objects, someone randomly pick things out of the bag, what is the probability he will pick a red object or a triangular object

1)there are 6 red objects and 8 triangular objects in the bag

2) there are three red triangular objects in the bag

I chose C, not sure tho!

Somebody plz tell me how solve such questions! thanks!

就是求三角形或红色的items在所有items里面的比例。（1）三角形8个，红色6个，但不知道有没有即是又是的情况（或者知道即不是也不是的情况也可以），不行。（2）只知道同时是的情况，不知道分别的情况，不行。（1）+（2），是三角形或红色items就是6+8-3。那么比例也就出来了

joannachou

以下是引用NKspielberg在2008-10-25 11:09:00的发言：

326. PS: the area of a circle is x, and the circle is inscribed in a square with parameter X. X equals to?

64/pai

How?

圓面積: x=pai*r²

^{so, r = 根號(x/pai)}

^{又正方形周長x=8*r}

^{代入r, 可解出x=64/pai}