(1) The deck is 2m wide, and encompasses a pond with radius 7.5m. The surface area of the deck is `pi(11.5)^2-pi(7.5)^2=76pi` .(Take the area of the pond and deck, and subtract the area of the pond.)

(2) The volume of concrete is found by `Ah` where `A` represents the area, and `h` the height or thickness. Here `A=76pi m^2` and `h=.15m`

So `V=76pi*.15=11.4pi~~35.8m^3`

**The required volume is approximately 35.8 cubic meters.**