Doubtnut, a Gurgaon-based startup that operates an app to help students learn and master concepts from math and science using short videos, has raised $15 million in a new financing round as it looks to serve more people in small cities and towns of the country.

The financing round, Series A, was led by Chinese giant Tencent. Existing investors Omidyar Network  India, AET, Japan and Ankit Nagori (founder of fitness startup Cure.Fit), and Sequoia Capital India  also participated in the round, the two-year-old startup said.

Doubtnut, part of Sequoia Capital India’s Surge accelerator, has raised $18.5 million to date, and its new financing round valued it at about $50 million, a person familiar with the matter said.

The app allows students from sixth grade to high-school solve and understand math and science problems in local languages. Doubtnut app allows them to take a picture of the problem, and uses machine learning and image recognition to deliver their answers through short-videos.

A student can take a picture of the problem, and share it with Doubtnut through its app, website, or WhatsApp  and get a short video that shows the answer and walks them through the procedure to tackle it.

Doubtnut said it has amassed over 13 million monthly active users across its website, app, YouTube, and WhatsApp . More than 85% of Doubtnut users today come from outside of the top 10 cities in India, said Tanushree Nagori, co-founder of Doubtnut. She said that more than half of these students have come online in the last one year.

“Doubtnut is truly democratizing education across India. Our user base reflects the entire demography of India, something which no other education app in the country has come close to achieving,” she said.

The growth of Doubtnut represents the emergence of a wave of startups in India that are tackling local challenges. In the education space alone, a number of players including Byju’s, which is now valued at $8 billion, Unacademy,  Vedanutu, and GradeUp have shown impressive growth.

Gaurav Munjal, founder and chief executive of Unacademy, said on Saturday that his startup’s one-year-old premium offering had clocked $30 million in revenue.