Question 874957
Area of the concrete path is {{{pi*7.7^2-pi*7^2}}} square meters, using 0.70 meter for 70 centimeters.
That area, {{{pi(7.7^2-7^2)}}}
{{{pi(7.7-7)(7.7+7)}}}
{{{pi*(0.7)(8.4)}}}
area is <b>18.47 square meters</b>.  You can apply the price of concrete.