median
don steward
mathematics teaching 10 ~ 16

Monday, 8 August 2011

lichenometry

people use the diameter or the rate of growth of lichen as a means of dating historical events


some formulas have been devised to enable dates to be estimated
simpler formulas assume a circular growth pattern

a Pisa test item (international test, M047) provided a formula used in studies of glaciers

d is the diameter of the 'circle' in mm.

t is the number of years after ice has disappeared



the test asked students to use the formula to find an estimate for a diameter after 16 years


another question might have been:
for what two values of 't' does this formula predict the same numerical value for 'd' as for 't'?

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