The cross-section of a trough of depth 36 cm is a trapezium ABCD where AB = 50 cm as shown. If the area of ABCD is 2250 cm2, find the length of CD in cm.
75 cm
Let the length of CD be x cm.
Area of ABCD = 12 x (AB +CD) x depth
12 x (50 + x) x 36 = 2250
50 + x = 225018
50 + x = 225018
50 + x = 125
x = 75
The length of CD is 75 cm.