Question

Two persons A,B have to speak at a function with $10$ other persons. If the persons speak at random order, the probability that A speak immediately before B is

• A. $\frac{1}{12}$
• B. $\frac{1}{3}$
• C. $\frac{3}{8}$
• D. $\frac{5}{6}$

Answer 1

The correct option is A $\frac{1}{12}$

Total number of random ways to speak=12!

For .._,AB,_... constituting AB as a single entity total favourable ways=11!

Probability=11!/12!=1/12