Solution to puzzle 81

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 Here is the solution to puzzle 81

The running track he took is in elliptical shape. The circumference or perimeter of an ellipse can be approximated as
π √(2 (a2+b2))

where a is semi-major axis and b is semi-minor axis.

So in our example, a is 200/2 = 100 and b is 50/2 = 25

So circumference = 22/7 *  √ 2 *  (1002+252)

= 22/7 *  √ 2 *  (10000+625) =458.15 m.

So Jenny is correct.

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