Practice more problem-solving at https://brilliant.org/TedEd/ Solution to Bonus Riddle: https://brilliant.org/tededautobiographical/ You’ve found Leonardo da Vinci’s secret vault, secured by a series of combination locks. Fortunately, your treasure map has three codes: 1210, 3211000, and… hmm. The last one appears to be missing. Can you figure out the last number and open the vault? Tanya Khovanova shows how. Lesson by Tanya Khovanova, directed by Artrake Studio. Thank you so much to our patrons for your support! Without you this video would not be possible! Show Less >>