An open-top rectangular water tank has a volume of 24 cubic meters. Its length and width measure 4 meters and 3 meters respectively. Neglecting the thickness of the tank walls, what is the total cost to paint both the interior and exterior surfaces if the painting charges are Rs. 10 per square meter?

Explanation

First, find the height of the tank using volume = length × breadth × height, which gives height = 24 / (4 × 3) = 2 meters. Then, calculate the surface areas to be painted: inner surfaces include the bottom (4 × 3 = 12 m²) and the four sides (2 × (4 + 3) × 2 = 28 m²), totaling 40 m². The outer surfaces include the bottom and four sides as well, but with the same dimensions, so the total outer surface area is also 40 m². Therefore, total area to paint = 40 + 40 = 80 m². At Rs. 10 per square meter, the total cost is 80 × 10 = Rs. 800.