Learn more: http://www.khanacademy.org/video?v=wblW_M_HVQ8
Proving an expression for the sum of all positive integers up to and including n by induction

Length: 3 minutes

Alternate Proof to Induction for Integer Sum

Length: 5 minutes

Writing Proportions

Length: 4 minutes

Coverting Repeating Decimals to Fractions 1