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MATH PUZZLE: Can you replace...

MATH PUZZLE: Can you replace the question mark with a number?

Correct answers: 669

The first user who solved this task is Gospodja Pufna.

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Child’s Birthday Wish

Child: "Mom, may I have a bicycle for my birthday?"
Mom: "Will it make you behave any better if I do?"
Child: "No, but I’ll behave over a wider area."

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Measurement of star size

In 1920, first U.S. measurement of the size of a fixed star was made on Betelgeuse, the bright red star in the right shoulder of Orion, which was found to be 260 million miles in diameter - 150 times greater than the Sun. Dr. Francis G. Pease made the measurement on the 100-inch telescope at the Mount Wilson Observatory using a beam interferometer designed by Professor A. A. Michelson. Betelgeuse was selected as the first test object since theoretical calculations had suggested that the star was unusually great in size. The apparent angular size of Betelgeuse was found to average about .044 arcseconds. Direct interferometer measurements can only be used with large stars. The majority of stars rely upon more indirect methods of determining stellar sizes.

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