Desks

A class has 20 students. The classroom consists of 20 desks, with 4 desks in each of 5 different rows. Amy, Bob, Chloe, and David are all friends, and would like to sit in the same row. How many possible seating arrangements are there such that Amy, Bob, Chloe, and David are all in the same row?

Result

n =  120

Solution:

n=5⋅ 4!=120n=5 \cdot \ 4!=120

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