A tank with rectangular base and rectangular sides, open at the top is to be constructed so that its depth is 2 m and volume is `8/m^3`. If building of tank costs Rs 70 per sq metres for the base and Rs 45 per square metre for sides. What is the cost of least expensive tank?

A tank with rectangular base and rectangular sides open at the top is to be constructed so that its depth is 3 m and volume is 75 m3. If building of tank costs Rs. 100 per square metre for the base and Rs. 50 per square metres for the sides, find the cost of least expensive tank.

A rhombus sheet, whose perimeter is 32 m and whose one diagonal is 10 m long, is painted on both sides at the rate of Rs 5 per square metre. Determine the cost of painting.

An open tank with a square base and vertical sides is to be constructed from a metal sheet so as to hold a given quantity of water. Show that the cost of the material will be least when the depth of the tank is half of its width.

How many cubic metres of earth must be dug out to sink a well 14 m deep and 4 m in diameter? What will it cost to plaster its inner surface at Rs 2.50 per square metre?

What is the cost of tiling a rectangular plot of length 600 m and breadth 400 m in the rate of Rs. 12 per hundred square metre.

Find the cost of fencing a square park of side 250 m at the rate of Rs.20 per metre.