Question 135729
The gist of this problem is realizing that, in order to get the area of the walkway, we subtract the area of a smaller circle from that of a larger one.  The larger circle has a diameter of 28 yd (2 yd larger than the 26 yd circle), minus the 26 yd circle.

So a 28 yd circle has a radius of 14 yd, and an area of 2 * pi * 14^2

The area of the 26 yd circle is 2* pi * 13^2.

(Radius is half of diameter).

So, the area of the large circle is 2 * pi * 196 = 1231 sq yd (approx)

and the area of the smaller is 2 * pi * 169 = 1062 sq yd (approx)

(Always thought there was a beauty to these two adjacent squares  169 and 196!)

So the area of the walk would be 1231 sqyd - 1062 sqyd = 169 sqyd

This has to be multiplied by $50/sqyd to find the cost:

<u>169 sqyd * $50/sqyd = $8450</u>

(For your future study of "dimensional analysis," can you see how even the "sqyd" cancels out?)