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Why do ballons fly away when you let go of them? We've got the answer.

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There is something incredibly neat about helium balloons! If you buy one at the circus or fair, you can hold its string and it will ride along above you. If you let go of the string, it will fly away until you can't see it anymore.

If you havĀ­e ever wondered why it flies away, then read on. In this edition of HowStuffWorks, you'll find out all about helium!