The cross-section of a water channel is a trapezium in shape. If the channel is 12 meters wide at the top and 6 meters wide at the bottom and the area of cross-section is 630 square meters, what is the depth of the channel (in meters)?  Choose the most appropriate option
A) 50  B) 60  C) 70  D) 80  E) 90
1/2 * d * (12 + 6) = 630   d = 70   The answer is 70.
<result>C</result>
The cross-section of a water channel is a trapezium in shape. If the channel is 12 meters wide at the top and 6 meters wide at the bottom and the area of cross-section is 630 square meters, what is the depth of the channel (in meters)?