XDF蓝皮书几道题求助！急急！

shiningmoon

蓝皮书上册，PS部分

P156T155

P154T137

P134T8

P161T184答案A为什么不对？

P163T196:Each of the integers from 0 to 9,inclusive,is written on a separate slip of blank paper and the ten slips are dropped into a hat.If the slips are then drawn one at a time without replacement,how many must be drawn to ensure that the numbers on two of the slips drawn will have a sum of 10?

A.3  B.4  C.5  D.6  E.7 

求助这道题的解题方法，谢谢

P165T211

P168T230

P169T237

请帮帮忙，谢谢各位高人！感激不尽！

yuwei1988

P134T8:

题意是说每个小时变为原来的四倍，上午10点是1/2,问什么时候是1/8？

1/8的4倍是1/2 ,则可知一个小时之前就上午九点时是1/8。