Question

A meeting is to be addressed by 5 speakers A, B, C, D, E. In how many ways can the speakers be ordered, if B must not precede A (immediately or otherwise)?

• A. $120$
• B. $24$
• C. $60$
• D. $5^4\times 4$

Answer 1

Answer: (C)

$60$

Meeting is to be addressed by $5$ speakers $a,b,c,d,e$

$5$ speaker can be address in $5!$ ways $=120$

Either $b$ can speak before a or after a

ways the speaker be ordered is $b$ must not precede $a=\frac{120}{2}=60$

$\therefore$ Answer is $60$ ways