A water storage tank has the shape of a cylinder with diameter 10 ft. It is mountain so that the circular cross-sections are vertical. If the depth of the water is 7 ft, what % of the total capacity is being used?
"It is mountain"? Oh! "mounted".
You are told the height of the tank but not the radius. Okay, just call that "R". What is the volume of a cylinder with radius R and height 10?
Finding the volume of the water is a little harder. You will need to integrate to find the area of a portion of a circle of radius R (> 7) up to a chord 7 ft above the base of the circle.