1

The length of the arc of a sector is equal to its radius. Work out the angle at the centre. [3]

2

A sector has an angle of $120^\circ$ at the centre. The perimeter of the sector is $40$ cm. Work out the radius. [4]

3

The ratio of the arc length of a sector to its perimeter is $2 : 5$. Work out the angle at the centre. [4]

4

A sector of radius $9$ cm has the same area as a semicircle of radius $6$ cm. Work out the angle of the sector. [3]

5

A sector has a perimeter of $20$ cm and an area of $16$ cm$^2$. Work out the two possible values of the radius. [5]