Question

The number of permutations of 1,2,3,4,5,6 such that pattern 12,23,34,45,56 do not appear in the permutation is ?

Answer 1

`25`

Explanation:

Number of permutations of 6 objects taken 2 at a time:

`(6!)/(4!) = 30`

`12,23,34,45,56`

is 5 permutations.

So:

`(6!)/(4!) - 5 = 25`