There are 7 children that are taking turns using the swing on a playground. How many different ways are there in which they each can use the swing where everyone gets exactly one turn? roscoe has 15 books on his summer reading list. He wants to choose 6 books to read in order from first to last. In how many ways can he do this? the student council has 15 students. They need to choose a president, vice president, secretary and treasurer for student council. In how many ways can the 4 different positions be appointed from the 15 students? thomas is creating a 7 digit passcode using the digits 0 through 9. How many 7 digit passcodes are possible if the numbers cannot be repeated?