Speed of the water = 20 km/h = 20000 meter/60 min
\(\therefore\) Length of water covered in 20 min
= speed x time
= \(\frac{20000}{60}\times20=\frac{20000}3\) meter
Radius of base of the pipe is r = 3/2 meter
\(\therefore\) Volume of water flow = Area of cross section x Length of water flow
\(=\pi\times(3/2)^2\times\frac{20000}3\) = 15000 π m3
Standing under depth = 16 cm = \(\frac{16}{100}\) m
\(\therefore\) Irrigation area = \(\frac{Volume\,of\,water\,flow}{Standing\,water\,depth}\)
\(=\cfrac{15000\pi}{\frac{16}{100}}\)\(=\cfrac{15000\times3.14}{\frac{4}{25}}\)
= 294375 m2
= 29.43 hactares
