Measure and increase your math brawn with this arithmetic speed game.

The rules are simple: the app will give you a math problem to solve and you have 20 seconds to do it.

Sometimes the problems are easy, like 2 + 2. Othertimes they are evil and mean, like 47.1 ÷ 721 (that's 0.0653 by the way).

Sounds hard, huh? It is. So the app is kind and gives you partial credit: you're graded on bell curve around the answer. This means you can be a little wrong but still get partial credit.

The trick is to develop the ability to solve seemingly very difficult math problems in your head using successive approximations. First get the order of magnitude right, then the next digit, then the next.

Once you develop this skill, every day problems will be a pleasure to solve and you'll be the first one in your group of friends able to split the check (sorry).

This app is great for engineers, scientists, students, and the rest of us who just want to keep our brains working well.

I hope you enjoy it!