哩幾題都係我自已諗既,冇ans,唔該大家幫一幫我
1.有7本唔同既書(abcdefg),而家要係到抽3本,問抽到既3本中同時有a同b書既prob.?
ans
2P2*5P1)/7P3 or (2C2*5C1)/7C3 ????
2.一個袋有5個oranges,6個apples
a.係袋拎3個生果,問第一個係orange,第3個係apple既 number of ways of arrangement?
ans:5P1*7P1*4P1 ?
b.抽3個生果,問抽到第一個係orange,第3個係apple既prob.
ans
5P1*7P1*4P1)/11P3 ???
3.個袋有5 black balls.6 white balls
a.拎2個balls,問係一個black ball,1個 white ball既 number of ways of arrangement?
ans:5P1*6P1 ????
b.抽2個波,問係一個black ball,1個 white ball既prob.
ans
5P1*6P1 )/11P2 or (5C1*6C1)/11C2 ?????
4.個袋有5個black balls,6個 white balls,而家抽5個,問抽到有2粒black balls同2粒white balls既prob.?
ans:(5P2*6P2*9P1)/11P3?
5.個袋有2red balls,1white balls,1 green balls and 2 blue balls
a.問no. of ways of arrangement?
b.抽5個波,問抽到2個blue balls,1 red ball,1 white ball and1green balls既prob.
我真係好唔明,好唔可以講得詳細D係用P定C?點解?
唔該各位
em46