I have a big question about permutation here. the first question, I can understand the way how to solve. but I used the same way to solve the 2nd question, it was wrong, please help me here!!! why I can't use the same way to solve the 2nd one??
(practice for gmat!)
question 1: 8 cars (3red, 3blue, 2 yellow)are to be parked in a line, how many unique lines can be formed if the yellow cars must not be together? assume that cars of each colors are identical.
I know how to solve this one. but 2nd one is harder!
question 2: how many ways can 8 books, each covering a different subject, be arranged on a shelf such that books on biology, history, or programming are never together?
8!-3!*5!= this is wrong, but I don't get it!
pls if you could help, I do need some help. thanks!