Four horses are tethered at four corners of a square plot of side 63 metres so that they just cannot reach one another . The area left ungrazed is
Four circular cardboard pieces , each of radius 7 cm are placed in such a way that each piece touches two other piece . The area of the space enclosed by the four piece is
If the circumference of a circle increases from ` 4 pi to 8 pi`, what change occurs in its area ?
If the radius of a circle is doubled its area is increased by :
If the radius of a circle is diminished by 10% , then its area is diminished by :