Useful numbers to memorize@Everything2.com

one year = 3e7 seconds - useful for those "if everyone on Earth did ~ one time every second" ideas
1 meter per second = 2.16 mph - this is useful for estimating speeds by sight.
one hour = 3600 seconds
one mile = 1.6 km (and one km = 0.6 miles - see golden ratio
speed of light in a vacuum = 3e8 m/s
one mile = 5280 feet
one square mile = 640 acres
one acre is ~ 209 feet on a side
one ounce = 28 grams
one kilogram = 2.2 pounds
(1 + 1/n)^n approaches e as n goes to infinity. So the sequence 1.5², 1.25⁴, 1.1¹⁰, 1.05²⁰ etc goes to e.
1 mb of mp3 = 1 minute of sound at 128 kbps

Golden ratio	Infinite expected value	gomi no sensei	English units / Metric conversion factors
Bingbang Babbaloo Battles Burpers	Quick unit conversion	mile	infinity
e	CPUID	The Birth of Conversion	Unit Conversion
Gravity	second	Russia	Currency of the World
Star Island	Unit conversion formulae	Everything Kitchen Conversion Table	Volume Conversion Factors
Area Conversion Units	Conversion Table

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