Task of the Week: Circles in the cobblestone

The task is Apolda, Germany.

Determine by what percentage the first circle with the dark stones is larger than the inner circle (light stones).

To get the solution of the task, one can make different models. On the one hand it is possible to count the light and dark stones and calculate the ratio. Another possibility is to calculate the area of a circle and a annulus.

It is not enough to calculate only the ratio of both stone types. To get the right result, the ratio must be converted to percent and then reduced by 100. Only then someone knows how many percent larger the annulus is than the inner circular area.

Thanks to MCM Educator Jörg Kleinsteuber for this task.