Popular language learning tool Duolingo just closed a $45-million funding round led by Google Capital, raising more than double the total amount of previous rounds.

Duolingo has so far proved widely successful, racking up more than 100 million users and attracting new ones each day. Duolingo currently ranks as the most downloaded application in the Education category on both Apple's App Store and Google's Play Store.

Duolingo's premise is that good tutors are hard to find — not to mention expensive. As a solution, the company aims to leverage technology, giving all people access to a personalized and effective learning experience.

At a valuation of $470 million, Duolingo has now raised an additional $45 million to boost its ambitious efforts. The new round of funding led by Google Capital also includes previous Duolingo investors such as Union Square Ventures, Kleiner Perkins Caufield & Byers, and New Enterprise Associates.

Previously, Duolingo raised $3.3 million in a series A round led by Union Square Ventures back in October 2011, $15 million in a series B round led by New Enterprise Associates (NEA)  in September 2012, and $20 million in a series C round led by Kleiner Perkins Caufield & Byers in February 2014.

This means that the latest round of funding led by Google Capital more than doubles the $38.3 million Duolingo previously raised in rounds A, B and C — reaching a total of $83.3 million. Duolingo aims to use the additional $45 million to launch new revenue experiments, as well as extending its free tutoring services to parts of the world that it hasn't so far reached.

As for existing markets, the company touts that more people are currently using Duolingo to learn new languages in the U.S. than in the public school system. Duolingo also claims that more than 100,000 teachers are registered for its free platform for schools.

The new funding will allow Duolingo to broaden its presence in more schools across the world, while also improving the platform to enhance the overall experience.

"Duolingo's mobile-­first, adaptive, and gamified platform is changing the way people are learning languages across the globe," said Laela Sturdy, partner at Google Capital. "We were blown away by Duolingo's growth and engagement numbers, and we're thrilled to partner with them as they shape the future of education."