Once you figure this out it'll blow your mind...

"The lines over the circles are color coded. Notice the single red line and 3 blue lines representing "13" grouped together while the single green and 2 black lines take their own group. [Simply] draw your first group of lines in one direction then your second group of lines going over the first, count the groups of intersections and there's your answer."


Further Explanation: http://scienceblogs.com/grrlscientist/2007/01/30/multiplication-using-lines/

Shared publiclyView activity