From The World and PRX, this is The Number in the News. Today’s number: 10,000. Zaatari, a Syrian refugee camp in Jordan, has quickly turned into a city of 80,000 people since opening in 2012. Water can be scarce and the desert soil is too poor to cultivate anything, making nutritious food a hard resource to come by. But scientists from the University of Sheffield in England have a solution. They're teaching refugees how to grow food by using old foam mattresses instead of soil. They have 10,000 mattresses on hand, and the UN Refugee Agency is training people how to use them. It’s working at the refugee camp, and it could be a solution used in cities around the world.