The Numbers of Epidemics and Why Keeping Cafes Open is More Important than High Schools

There’s this old joke/riddle/maths puzzle: an algae is spreading in a lake so that every night, the covered area doubles. After 10 weeks, 70 days, the lake is fully covered. After how many days was the lake halfway covered? The correct answer is, of course (but very counter-intuitively), that it is half-covered after 69 days […]

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