Four cows are tethered at four corners of a square plot of side 50m, so that they just cannot reach one another. What area will be left un-grazed?

A rectangular piece is 20m long and 15m wide. From its four corners, quadrants of radii 3.5m have been cut. Find the area of the remaining part.

Four equal circles, each of radius 5cm, touch each other as showing fig.15.65. Find the area included between them.

Four equal circles, each of radius a, touch each other. Show that the area between them is.

A square water tank has its side equal to 40m. There are four semi-circular grassy plots all round it. Find the cost of surfing the plot at Rs.1.25 per square meter.