Why is volume calculated in units cubed?

Please help asap for 100 pointsss~

At a sand and gravel plant, sand is falling off a conveyor and onto a conical pile at a rate of 16 cubic feet per minute. the diameter of the base of the cone is approximately three times the altitude. at what rate is the height of the pile changing when the pile is 12 feet high? (hint: the formula for the volume of a cone is v = 1 3 πr2h.)

The water has been on the stove y=9.5x+62.1 after how many minutes will the tempature be 138.1 f

Choose the correct slope of the line that passes through the points (1, -3) and (3, -5)