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?

Answer 1

the school bus has                         = 25 seats
number of rows                              = 5 rows
number of seats in an row             = 5 seats
number of first grade students       =15 students
number of second grade students =5 students

so,now  if the second grade students occupied the first row ,they can occupy becoz only 5 second grade students are there and 5 seats in each row                      
now,the first grade students can occupy the first 3 rows or last 3 rows or they can sit where ever they want except 1st row.becoz they hv 20 seats left.                    

Answer 2

5P5 × 20P15 

hope it helps you

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