Question

a circular pool measures 10 ft across. 1 cubic yard of concrete is to be used to create a circular border of uniform width around the pool. if the border's depth is 2 inches, how wide would will it be?

Answer 1

volume of stuff is 2 inches times (area of outer circle - area of inner circle)

22 inches = 1/6 foot
1 yard^3 = 27 ft^3

so
27 = (1/6)(pi)(R^2 - 5^2)

solve that for R
then width of path = R-5 in feet

Answer 2

2 inches = 1/6 foot