don steward
mathematics teaching 10 ~ 16

Sunday, 29 March 2009

hairy thoughts

how fast do you think your hair grows, in km per hour?

on average, hair grows at 1.44 cm every 30 days (well, between 1cm and 2 cm anyway)
how much is this per day?
per hour?
so this is the length your hair will have grown by the end of this one hour lesson....

now let's convert cm per hour into km per hour
on some calculators this is shown in standard form
what's this in km per minute?
in km per second?

according to figures published by Drs. Erasmus Wilson, Withof & Stelwagon in the nineteenth century (and therefore in inches)
blonde 146000 hairs per head, diameter measuring 1/1500th - 1/500th in.
black 110000 hairs per head, diameter measuring 1/400th - 1/250th in.

assuming a hair is a cylinder, estimate the average length of your hair and use this to work out an approximation for the volume of hair on your head [1 in. = 2.54cm]

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