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Calculate the number 6669

NUMBERMANIA: Calculate the number 6669 using numbers [1, 5, 8, 5, 80, 817] and basic arithmetic operations (+, -, *, /). Each of the numbers can be used only once.

Correct answers: 25

The first user who solved this task is Djordje Timotijevic.

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What do you do when 50 zombies surround your house?
- Hope it's Halloween.

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Pen

In 1809, the first patent was issued in the U.S. for a metallic writing pen was issued to Peregrine Williamson a jeweller of Baltimore, Maryland. The patent title occurs in summary lists in published books that exist after the fire that consumed all the records at the Patent Office on 15 Dec 1836. Williamson's pens were made of steel rolled from wire, a sort of steel quill that would never need cutting to sharpen the nib. His first attempt did not write well for want of flexibility but that was solved by adding two more slits parallel to the main one. He then had a product that eventually sold so well it kept him and a journeyman employed full-time in a profitable business. There are references to steel pens being used in Britain before this patent.«

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