A water trough is 10 meters long and the cross-sections have the shape of an isosceles trapezoid that is 30 cm wide at the bottom and 80 cm wide at the top with a height of 50 cm. If the trough is being filled with water at the rate of 0.2 cubic meters per minute, how fast is the water level rising when the water is 30 cm deep? Area of a trapezoid is A=1/2(b1+b2)h. So volume of the trough is the area of the ends times the length.