大牛注意：“费时易错”机经总结讨论！！---??

redpot

13.100-999的三位数，不含2，5的有多少个？（7*8*8＝448）
How to get it?

22.1圆盘有八数字(有图),求三连续为16 的可能数.
Any detail about it?

23.1982年，June 25 是星期五，1987年，June 25是星期几？
I got it as Tuesday.  How comes?

24.For all x, x is positive integer, \"2-height\" is defined to be the greatest nonnegtive n of x, what is the greatest number of 2-height when 2^n (2的n次方) is the factor of x?
A. 2
B. 12
C. 40
D. 76
E. 90
C. 40（各选项质因数分解后，指数最大者）
I can't get it.

27.已知抛一种硬币落地的正反面概率不是1/2，问抛两次硬币都是正面朝上的
概率是多少？
1) 每抛一次，正面朝上的可能性是反面的朝上的两倍
2) 抛两次，一正一反的概率是4/9 答案A
What is wrong with 2?

Thanks a lot!

tongxun

13.100-999的三位数，不含2，5的有多少个？（7*8*8＝448）
How to get it?
---------------------
1\3\4\6\7\8\9\0; first unit can not be 0,so 7 choices, second and third 8; the answer is 7*8*8

22.1圆盘有八数字(有图),求三连续为16 的可能数.
Any detail about it?
---------------
1: 1,7,8,---p3,3
2: 2,6,8; 2,7,7 p3,3 +p3,3/p2,2
3: 3,5,8; 3,6,7, p3,3 + p3,3
4: 4,4,8; 4,5,7, 4,6,6 p3,3/p2,2 +p3,3 +p3,3/p2,2
5: 5,5,6 p3,3/p2,2

23.1982年，June 25 是星期五，1987年，June 25是星期几？
I got it as Tuesday. How comes?
------------
(365*4+366)/7  the reminder is 6, Friday +6= Thursday
24.For all x, x is positive integer, \"2-height\" is defined to be the greatest nonnegtive n of x, what is the greatest number of 2-height when 2^n (2的n次方) is the factor of x?
A. 2
B. 12
C. 40
D. 76
E. 90
C. 40（各选项质因数分解后，指数最大者）
I can't get it.
----------
If you can not work out such question, just remenber 40. 40=2(3 ci fang)*5 ,3 is the biggest **

27.已知抛一种硬币落地的正反面概率不是1/2，问抛两次硬币都是正面朝上的
概率是多少？
1) 每抛一次，正面朝上的可能性是反面的朝上的两倍
2) 抛两次，一正一反的概率是4/9 答案A
What is wrong with 2?
-------------
2) 正面朝上的概率是?

Thanks a lot!

redpot

Thank you very much.  I got it.