Question

The cross section of a canal is in a shape of a trapezium. If the canal is 12 m wide at the top and 8 m wide at the bottom and the area of its cross – section is 84 $m^2$, determine its depth.

• A. 9.4 m
• B. 6.8 m
• C. 7.2 m
• D. 8.4 m

Answer 1

The correct option is D

8.4 m

Area = 84 $m^2$ (given), a = 12 m and b = 8 m

So, $\left(\frac{1}{2}\right)$ (a + b)h = 84

$\Rightarrow$ $\left(\frac{1}{2}\right)$ (12 + 8)h = 84

$\Rightarrow$ h =$\frac{84\times 2}{20}$ = 8.4 m