draw two altitudes from the lower corners of the trapezoid to the upper base.A water trough is 4 m long and its cross-section is an isosceles trapezoid which is 80 cm wide at the bottom and 120 cm wide at the top, and the height is 40 cm. The trough is not full. Give an expression for V, the volume of water in the trough in cm3, when the depth of the water is d cm.

sketch in a horizontal water level of depth d.

note the similar right triangles on either end ... let x = horizontal water level distance from the altitude to the trapezoid's nearest side

water level cross-sectional trapezoid area ...

Volume in ...