Question

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 $840sq.m$, the depth of the canal is:

• A. $8.75m$
• B. $42m$
• C. $63m$
• D. $84m$

Answer 1

The correct option is D $84m$

Let the depth be x

$\frac{x}{2}(12+8)=840$

$\frac{x}{2}\times 20=840\Rightarrow x=84m$