Question

A gentleman has 6 friends to invite. In how many ways can he send invitation card to them if he has three servants to carry the cards?

Answer 1

Given, that a gentleman has 6 friends to invite but he send invitations to them if he has 3 servants. He send to invitations to one of his friends in 3 different ways 

Similarly he send invitations to them if has 3 servants = 3 × 3 × 3 × 3 × 3 × 3 = 3⁶ = 729