the cross - section of a cannel is a trapezium in shape . if the cannel is 15 m wide at the top and 4 m wide at the bottom and the area of cross - section is 1900 sq m , the depth of cannel is ?
"1 / 2 * d ( 15 + 4 ) = 1900 d = 200 answer : b"
divide(divide(divide(1900, divide(add(15, 4), const_2)), 4), const_2)