Replace the question mark with a number
MATH PUZZLE: Can you replace the question mark with a number?Correct answers: 70
The first user who solved this task is Eugenio G. F. de Kereki.
#brainteasers #math #riddles
CarborundumIn 1893, carborundum was patented by Edward G. Acheson of Monongahela, Penn. He had discovered it accidentally while trying to make artificial diamonds. He had dissolved carbon into molten corundum (a mixture of powdered coke and clay) in an electric furnace, and that yielded dark, hard, gritty crystals. He named the new material carborundum, and found it was one of the hardest industrial substances (second only to diamond), which made it an excellent abrasive material. In 1894, he started the Carborundum Company in Monongahela to produce grindstones, knife sharpeners, and various abrasives. Later, on 19 May 1896, obtained a patent for an electric furnace, suitable for making carborundum.« |