The first exercise deals with

circumference = 2 pi r

Area= pi r"2

the following exercise is done by these formulas.....using sectors....

the radius & the angle of the sector is given then

area of the sector = A/360 * pi r "2

Length of the arc of the sector= A/360 * 2 pi r

In many cases, for example, if asked to find the area of a shaded portion of a circle. First find the total area of the circle and the other inside it(not the shaded region)using these formula,and subtracting ar(circle) by ar(other region).Then you get the area of the given shaded region inside it.

Questions are not usually direct as this.

DBT JRF EXAMINATION