World Maths Day Contest: March 5

On WorldMaths Day, students aged 4-18 years old team up to solve arithmetic and mental computation problems together in real time.
Open to schools, individuals, and homeschoolers alike, this free global event awards minted medals, world cups, and prizes, and recognizes each participant with a certificate.
Begun in 2007, World Maths Day has "united the world in numbers" ever since. 
This year's World Maths Day starts in the U.S. on the morning of Tuesday, 5 March, with challenges lasting for as long as an hour or as little as one minute.
Freely downloadable PDFs include a teacher guide, World Education Games poster, and Frequently Asked Questions.

Check out the World Maths Day's first ever apps for Apple iPadand iPad Mini or for the Android math app.