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Very Old Man

Age 16 to 18
Challenge Level Yellow star
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Li Ching-Yuen himself gave a hint as to the secret of long life. It was

* Keep a quiet heart * Sit like a tortoise * Walk sprightly like a pigeon * Sleep like a dog

If this hint is not enough to help, try plotting the data on a chart. If there is a 50% chance, say, of death each year, by what factor might the expected numbers of living very old people reduce over 5 years? Can you find a percentage which might fit the data?


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The NRICH Project aims to enrich the mathematical experiences of all learners. To support this aim, members of the NRICH team work in a wide range of capacities, including providing professional development for teachers wishing to embed rich mathematical tasks into everyday classroom practice.

NRICH is part of the family of activities in the Millennium Mathematics Project.

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