Ralph has seven different colors of leftover paint Since the

Ralph has seven different colors of leftover paint. Since there is not enough of any one color to paint all four walls of his room, he has decided to paint each wall a different color. How many different ways can he carry out his plan?

Solution

Number of ways of painting 4 walls using 7 paints = 7P4

= 7!/(7 -4)!

= 7!/3!

= 7 * 6 * 5 * 4

= 840 ways