This video shows how the Japanese multiplication algorithm (sometimes called Vedic multiplication) which uses lines and their intersections to multiply two positive integers. It also shows the algorithm can be used to multiply numbers in other bases. Shaun Klassen of Math Concepts Explained has also written a post about it.
Some things to think about:
- Why does the method work?
- What basic geometric concept does this algorithm relate to?
- What if the numbers you multiply contains zeroes?