Philadelphia will be the proving ground for a series of apps designed to help adult learners become fully literate.

XPRIZE — the nonprofit known for holding ambitious public competitions — has picked eight mobile tools that are supposed to aid adults who read below a third-grade level. The tools will be tested over the next year in Philadelphia, Dallas, and Los Angeles, with more than 12,000 adults taking part in the trials.

The app that produces the largest learning gains will earn $3 million, with smaller prizes awarded to teams that do best with specific demographic subgroups.

The eight entrants come from across the globe.

A team out of Amrita University in India created a tool that harnesses the power of smartphone games to impart literacy and life-skill lessons. The creators said their app has already touched 300,000 users on the subcontinent.

Cell-Ed out of Oakland, California provides courses by audio and text that can be accessed on a basic cell phone without internet access. Meanwhile, the Lyriko team from Cambridge, Massachusetts encourages adults to build literacy skills through song lyrics.

xprise-2Shivsubramani Krishnamoorthy (left) and his colleagues at Amrita University in India are competing for the $7 million Barbara Bush Foundation Adult Literacy Xprise. (Emma Lee/WHYY)

There are 36 million American adults considered to have "low literacy" skills, according to a 2015 report from the U.S. Department of Education. Low-literate adults are those who can do little more than "complete simple forms, understand basic vocabulary, determine the meaning of sentences, and read continuous texts with a degree of fluency," according to the study.

This particular XPRIZE competition is a departure for the organization, which made its name on high-tech, high-cost contests to build things like private spacecrafts and uber-efficient cars.

XPRIZE's senior director for the competition, Shlomy Kattan, said the nonprofit zeroed in on adult literacy because it's an area of big need and small investment. Given how little governments spend on adult literacy — compared to, say, pre-K or K-12 education — Kattan said there's room for a well-designed app to make a major difference in people's lives.

"Any time that you can do anything to invest in people who generally have been left behind and pushed to the back, it's a beautiful thing," said Kattan.

Money for the competition came from Barbara Bush Foundation and the Dollar General Literacy Foundation, among other organizations.