How to multiply with multiples of nine - calculating the fast way with this cool math trick! Multiples of nine include numbers such a eighteen, twenty seven, thirty six and so on. To do this technique using this math lesson, you change the number that is a multiple of nine into an easier nearby tens number - and then you'll be calculating with speed and accuracy. To donate to the tecmath channel: To donate to the tecmath channel: To support tecmath on Patreon: To buy tecmath mechandise: