Consider an area of cross-section of canal as ABCD.
Area of cross-section = 6 × 1.5 = 9 m2
Speed of water = 10 km/h = 10000/60 meter/min
Volume of water that flows in 1 minute from canal
= 9 x 10000/60 = 1500 m3
Volume of water that flows in 30 minutes from canal
= 30 × 1500 = 45000 m3
Let the irrigated area be A. Volume of water irrigating the required area will be equal to the volume of water that flowed in 30 minutes from the canal.
Vol. of water flowing in 30 minutes from canal = Vol. of water irrigating the reqd.
45000 =(A x 8)/100
A = 562500 m2