11th Grader Invents a Flashlight Powered by Body Heat

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11th Grader Invents a Flashlight Powered by Body Heat
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Think about that for a moment: a flashlight that shines for as long as you hold onto it. No more scrambling for and chucking away AA batteries. It could have an immediate impact on more than 1.2 billion people -- one-fifth of the world's population -- who, according to the World Bank, lack regular access to electricity.

Stunningly, no one on record has thought to use thermoelectric technology to power a flashlight. But for Ann, peltier tiles, which produce an electrical current when opposite sides are heated and cooled at the same time, were a convenient solution to a friend's study problem.

The Math Behind PIzza

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The Math Behind PIzza
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The math of why bigger pizzas are such a good deal is simple. A pizza is a circle, and the area of a circle increases with the square of the radius.

So, for example, a 16-inch pizza is actually four times as big as an 8-inch pizza.

And when you look at thousands of pizza prices from around the U.S., you see that you almost always get a much, much better deal when you buy a bigger pizza.
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