Question

A school bus has 25 seats, with 5 rows of 5 seats. 15 students from the first grade and 5 students from the second grade travel in the bus. How many ways can the students be seated if all of the second-grade students occupy the first row?
25P20
5P5 × 20P15
5C5 × 25C14
5P5 × 15P15
5P5 × 25C15

Answer 1

i never saw this before

Answer 2

@Donblue22

Answer 3

@perl

Answer 4

http://openstudy.com/study#/updates/52656b72e4b029b030da278c Its the same question and it tell you the solution :)