trying to tackle the world's education divide one language at a time with his free language learning ap duolingowe met up with him at his headquarters in pittsburgh to talk to him about why transparency is so important to growth and how he's gotten everyone from students in columbia to tom hangs using the app. >> education always thought of this thing that creates a huge gap between social classes. most of the ways to learn a language before duolingo was very expensive. the irony was most people were trying to get out of poverty. we decided to launch duolingo in the year 2012. everybody that came here came because of the mission, or most everybody. they had offers from other companies that five years ago had much bigger names than us. somebody who doesn't have a bank account should be able to have access to all of our learning. we know if we charge people for our app we could be making more money. but we've decided no the to do that. instead we put an ad at the end of every lesson. we also allow people to really, really don't like ads you can pay to remove ads. the main thing we think about is h