the cross - section of a water channel is a trapezium in shape . if the channel is 12 meters wide at the top and 8 meters wide at the bottom and the area of cross - section is 700 square meters , what is the depth of the channel ( in meters ) ?
1 / 2 * d * ( 12 + 8 ) = 700 d = 70 the answer is c .
divide(700, divide(add(12, 8), const_2))