21 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 from the following options:
A) 625
B) 600
C) 576
D) 676
E) 420
we can go in any bus out of the 21 buses.   Hence He can go in 21 ways.   Since we can not come back in the same bus that he used for travelling,   we can return in 24 ways.   Total number of ways = 21 x 20 = 420   ANSW420R:420
<result>E</result>
21 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?