23 buses are running between two places P and Q. In how many ways can a person go from P to Q and return by a different bus? Choose the correct choice.
A) None of these B) 506 C) 512 D) 524 E) 542
Explanation :   He can go in any bus out of the 23 buses.   Hence He can go in 23 ways.   Since he can not come back in the same bus that he used for travelling,   He can return in 22 ways.   Total number of ways = 23 x 22 = 506. Answer : Option 506
<result>B</result>
23 buses are running between two places P and Q. In how many ways can a person go from P to Q and return by a different bus?