Monthly Archives: March 2012

Basics of Combinations

First make sure to read the basics of permutations. So what’s the different between permutations and combinations? Suppose we have set A = {a,b,c,d,e}. A permutation of that set could be abc, and another permutation could be acb. In other words, a permutation is an arrangement of the objects of set A, where order matters. […]

Proving that 1/8 Is Larger Than 1/4

Yep, you’ve read that right. Here we go (log below means log10, so log with base 10): 3 > 2 3 log(1/2) > 2 log(1/2) log[(1/2)³] > log[(1/2)²] (1/2)³ > (1/2)² 1/8 > 1/4 Convinced? If not, what’s wrong with the proof above? Click to see solution In reality log10(1/2) is negative, so the second […]

Basics of Permutations

In how many ways can you arrange a group of 4 items? Most people (well, programmers at least) know the answer for that is 24, which is 4!. But what about the more generic case where you have n items and want to permutate only k of them at a time, how many permutations are […]