the cross - section of a cannel is a trapezium in shape . if the cannel is 8 m wide at the top and 2 m wide at the bottom and the area of cross - section is 770 sq m , the depth of cannel is ?
"1 / 2 * d ( 8 + 2 ) = 770 d = 154 answer : c"
divide(divide(divide(770, divide(add(8, 2), const_2)), 2), const_2)