In how many ways can five examination papers be arranged so that physics and chemistry paper never comes together?

Dear Student
Total ways for arranging five papers = 5!
= 120

Total ways in which physics and chemistry comes together = 4! (2)
= 48

Total ways in which five examination papers be arranged so that physics and chemistry paper never comes together =
Total possible ways –Total ways in which physics and chemistry comes together

= 120 –48
= 72

Thanks