Question

Jing jing works in a store and she spends some of her time organizing the stationary section. If there are nine different items on the rack, how many ways can she organize the rack so that the two most expensive items are not together?

Answer 1

282240 ways

Explanation:

number of items = 9 different items

Ranking based on worth

determine number of ways to arrange the 9 items such that the 2 most expensive are apart

first step: consider the 2expensive items as 1

∴ number of permutation = [ ( 9 - 2 ) + 1 ]! * 2!

= [ 8 ] ! * 2! = 80640

Total number of permutation/arrangement = 9! = 362880

hence to arrange the 9 items without having the two most expensive items together

= 362,880 - 80640

= 282240 ways