A cylindrical tank with a given volume V (V is constant) is to be made without a lid. The
material for the bottom costs five times as much per unit area as that for the sides. What
should be the ratio of the height to the radius for minimum cost?
A wire 20 inches long will be cut into two parts, one to be bent to form a square and the other to form a circle. What is the side of the square and the diameter of the circle so that the combined area is least?