A concrete loading ramp is a solid whose cross-section is a right triangle rising 1.5 m over a horizontal run of 8 m, and the ramp is 3.5 m wide throughout. Concrete costs ₹4200 per cubic metre. What does the ramp cost?

The cross-section measures $(1/2)\times 8\times 1.5=6$ sq m, and a solid of constant cross-section holds cross-section $x$ width = $6\times 3.5=21$ cubic m. The cost = $21\times 4200$ = ₹88200. The trap ₹176400 prices 42 cubic m, having dropped the 1/2 and made the ramp a cuboid; ₹29400 prices 7 cubic m, applying a pyramid's 1/3 to a shape that keeps the same cross-section all the way across; ₹25200 prices the 6 sq m cross-section itself and never brings in the 3.5 m width.