Permutations and school timetable If there are 6 periods in each working day of a school. In how many different ways can one arrange 5 subjects such that each subject is allowed at least one period? I tried this way- One of the six periods can be arranged in 5 ways and the remaining 5 periods in 5 factorial ways. Totally 600 ways

There can be 5 cases as the mentioned case below
S1,S2, S3, S4, S5, S1 which can be arranged in 6!/2! ways.
Required no of ways will be 
5× 6!/2! =1800
