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How many 5-digit numbers (it...

How many 5-digit numbers (it cannot start with 0) are there that do not contain the numbers 3 and 5, and are multiples of 4?

Correct answers: 23

The first user who solved this task is Manguexa Wagle.

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Doctor: What’s wrong with y...

Doctor: What’s wrong with your brother?
Boy: He thinks he is a chicken.
Doctor: really? How long has this been going on?
Boy: Five years.
Doctor: Five years!
Boy: We would have brought him in earlier, but we needed the eggs.

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First xenon compound

In 1962, the first compound of any “inert gas” was made by Neil Barlett by reacting platinum hexafluorideand xenon to form XePtF6, a yellow-orange solid that was stable at room temperature. The previous autumn, he had prepared a remarkable compound of oxygen with platinum hexafluoride. In that compound, [O2]+[PtF6]–, the platinum hexafluoride, PtF6 was such an extreme oxidizer that the oxygen formed a positive cation. Interestingly, the energy to remove an electron from oxygen (12.2 eV), he realized, was extremely close to that for xenon (12.13 eV). This suggested a xenon compound could be made in a similar way. His success ended the half-century belief that xenon was an inert gas, and is since known as a “noble” gas.«

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