The cross section of a canal is trapezium in shape. The canal is 12m wide at the top and 8m wide at the bottom. If the area of the cross section is 840 sq.m, the depth of the canal is: Options.
A) 42 m B) 84 m C) 63 m D) 8.75 m E) 9.75 m

Rationale: ½ ( 12 + 8 ) d = 840 or d = 84 m answer : b
Answer: B