The popular language learning app is betting that its gems, streaks and leaderboards will teach elementary school children—and adults—basic math.

A professor emeritus of mathematics explains why instruction on fractions needed to change.

Interventions for students struggling in math at any grade—not just elementary levels—should include at least 10 minutes per class dedicated to building fluency in basic math facts.

“Yes, you need to learn basic arithmetic and that’s part of the curriculum, but we also want kids to be able to use the arithmetic, be able to use the math,” she said.