I need help with this probability problem

Question

Let’s say that there are 26 people and 9 tables with 3 chairs at each table. Each person is assigned a seat at random. 2 of the people are friends. What is the probability that the 2 friends will sit at the same table?

Answer 1

Hi Ang B.,

Look, don't solve this as a combinations problem. Unnecessary commotion! Start with an empty room. Put the first friend in, (s)he gets a chair, right? Now let the second friend come in and randomly take a seat. How many seats were available? 26, right? So two of those seats were at the table with friend #1, so 2*1/26=P. The other people are totally irrelevant; though perhaps the teacher may want to keep the two friends separated .....?

Hint: Always look for the easiest way to visualize a problem.

-- Cheers, -- Mr. d.