You have 2 essay questions for an exam. There are 6 essays to choose from. How many different groups of 2 essays could you possibly choose?

Answer 1

There's a nice formula to figure this out, generally referred to as "n choose k". The formula is n choose k = n! / ( k! (n-k)! ). In your case n is 6 and k is 2, so we have 6 choose 2 = 6! / (2! x 4!) = 720 / (2 x 24) = 15.