jump to navigation

Problem of the Day #328: Movie Seats February 10, 2012

Posted by Alex in : potd , trackback

Albert and his 8 twin brothers are going to the movies and all wish to sit in the same row. The row contains 20 vacant seats. Albert and his twins want to seat themselves such that each person occupies exactly one seat and at least one of the seats at the end of the row is occupied. How many ways can they do this? Assume that Albert and his twins are indistinguishable.

Comments»

1. katherine - February 14, 2012

show

2. Saketh - February 29, 2012

Hi Katherine!

It looks like you have a good start there, but unfortunately your answer is not quite correct. Perhaps you could explain your reasoning?

Keep in mind that the answer is clearly at most (20 choose 9) = 167960.