Question

The cross-section of a canal is a trapezium in shape.If the canal is 10 m wide at the top 6 m wide at the bottom,and the area of the cross-section is 72 $m^2$,determine its depth.

Answer 1

Area of cross-section=72 $m^2$

Parallel sides of the trapezium= 10 m and 6 m

Let h be the depth of the canal

$\therefore Area=\frac{1}{2}\left(Sumofparallelsides\right)\times depth\Rightarrow 72=\frac{1}{2}(10+6)h\Rightarrow 72=\frac{1}{2}\times 16h\Rightarrow 8h=72\Rightarrow h=\frac{72}{8}=9m\therefore Depthofthecanal=9m$