Question

If $n$ books can be arranged on an ordinary shelf in $720$ ways, then in how many ways an these books be arranged in a circular shelf ?

• A. $120$
• B. $720$
• C. $360$
• D. $60$

Answer 1

The correct option is A $120$

$n$ books can be arranged in $N!$ ways

Given: $n!=720=6!$

Therefore, $n=6$

The number of ways books can be arranged in circular shelf $=(n-1)!=5!=5\times 4\times 3\times 2\times 1=120$

Hence the correct answer is $120$.