l两道Preceton Math

cathyyan

向牛牛求解题过程：

1.A part of game. foure people must each secretly select an integer between 1 and 4, inclsive, what is the approximat likehood that all four different pepole choose differenct number.
a) 9%
b)12%
c)16%
d)20%
e)25%
answer: a


2) out of 7 models, all of different hights, 5 models will be to chose to pose a photograph, if the 5 modes will be stand in a line from shortest to tallest,and the 4the tallest and 6 talles can not be adjacent, how many of 5 arrangement are possible.
a)6
b)11
c)17
d)72
c)210
answer: c