A cylindrical tank of radius $$10 \mathrm{~m}$$ is being filled with wheat at the rate of $$200 \pi$$ cubic metre per hour. Then, the depth of the wheat is increasing at the rate of

Water is being filled at the rate of $$1 \mathrm{~cm}^3 / \mathrm{s}$$ in a right circular conical vessel (vertex downwards) of height $$35 \mathrm{~cm}$$ and diameter $$14 \mathrm{~cm}$$. When the height of the water levels is $$10 \mathrm{~cm}$$, the rate (in $$\mathrm{cm}^2 / \mathrm{sec}$$) at which the wet conical surface area of the vessel increases is

A running track of 440 ft is to be laid out enclosing a football field, the shape of which is a rectangle with a semi-circle at each end. If the area of the rectangular portion is to be maximum, then the lengths of its side are

A spherical balloon is filled with 4500$$\pi$$ cubic meters of helium gas. If a leak in the balloon causes the gas to escape at the rate of 72$$\pi$$ cubic meters per minute then the rate (in meters per minute) at which the radius of the balloon decreases 49 min after the leakage began is