1 word = 20 grains of rice?
That's not very much at all. On average (from what I've always been taught), there are around 7,500 grains in one cup alone. Not to take anything away from their effort, but...
Note: There's a game on the Internet that donates money for rice to help with world hunger. Every time you answer a vocabulary question correctly, the site donates 20 grains of rice. If you could answer 12 questions correctly every minute you play, you'd have to play about 30 minutes to earn a cup of rice.
http://www.freerice.com
You'd have to play for a half hour, getting one correct word every 5 seconds just so someone gets ONE cup of rice? Eh, I'd rather just buy the rice and donate it, thanks.