Question

the cross section of a canal is in the form of a trapezium. if the top of a canal is 15m wide the bottom is 8m and the area of a cross section is 138 m2 find its depth

Answer 1

Top length of the canal, a = 15 m
Bottom length of the canal, b = 8 m
Let depth be 'h'
$area = \frac{1}{2} h(a + b) \\ 138 = \frac{1}{2} \times h \times (15 + 8) \\ h = \frac{138 \times 2}{23} = 12 \: m$