Q.Suppose a van seats seven people. In how many arrangements can seven people be seated if only four of the seven can drive

ANS : As only four of the seven can drive, therefore there are 4P1 ways to to select driver = 4

and then except that one who drives, 6 can be seated in  6P6 ways = 720

so in all seven people can be seated in 720 * 4 =  2880 ways