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?

A) 25P20
B) 5P5*20P15
C) 5C5*25C14
D) 5P5*15P15
E) 5P5*25PC15

Answer 1

It's option B

Explanation:

B. 5P5 × 20P15

Answer 2

Number of ways the second grade students can sit on the first row is 5! = 5P5
Number of ways 15 first grade students can sit in the remaining 20 seats is 20P15

Therefore, required number of ways is 5P5 * 20P15. (option B)