Question

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

Answer 1

$let \: \: a = 15 \: \: \: \: b = 8 \\ height \: \: be \: \: h \\ area = \frac{1}{2} h(a + b) \\ \frac{1}{2} h \times (15 + 8) = 138 \\ h = \frac{138 \times 2}{15 + 8} = 12 \: m$