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Calculate the number 2100

NUMBERMANIA: Calculate the number 2100 using numbers [9, 4, 9, 1, 39, 880] and basic arithmetic operations (+, -, *, /). Each of the numbers can be used only once.

Correct answers: 21

The first user who solved this task is Djordje Timotijevic.

#brainteasers #math #numbermania

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John Ramsey: Old Security Passwords

So they ask me, Would you like to answer your secret security password question? I think, Oh yeah, surely I can answer a question posed by slightly younger me.

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Sir James Gray

Born 14 Oct 1891; died 14 Dec 1975 at age 84.English zoologist who played a leading part in changing the main objective of 20th-century zoological research from evolutionary comparative anatomy to the functional analysis of living cells and living animals, particularly through his editorship (1925-54) of the Journal of Experimental Biology. He authored How Animals Move (1953), and Animal Locomotion (1968). Gray applied mechanical principles to the analysis of animal movement. In 1936, his calculations started a controversy, called Gray's paradox, concerning comparisons of swimming efficiency in fish and in submarines. Energetics calculations suggest that fish and other ocean denizens are much more efficient swimmers than subs, while theoretical hydrodynamic calculations suggest they are not.

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