Question

In how many ways can five examination papers be arranged so that physics and chemistry papers never come together.

• A. 31
• B. 48
• C. 60
• D. 72

Answer 1

Answer: (D)

72

Answer 2

Total arrangements of 5 papers are $= 5\mspace{6mu}! = 120$

When physics and chemistry come together

$= 4\mspace{6mu}!\mspace{6mu} \times 2\mspace{6mu}! = 48$

Hence required number of ways are $120 - 48 = 72$.