Answer:
10,995.6 ft^3.
2300.3 gallons.
(both to the nearest tenth).
Step-by-step explanation:
Area of the surface of the river = area of the outer circle - area of the inner circle.
Radius of the outer circle = 30 *3 = 90 feet.
So the surface area of the river = π(90)^2 - π(85)^2
= 875π ft^2
Also the volume of the river = surface area * depth = 875π*4 = 3500π ft^3
= 10,995.6 ft^3.
Number of gallons of water it will hold = 10,995.6 / 4.78
= 2300.3 gallons.