Answer:
see explanation
Step-by-step explanation:
Using the ratio equality for circles
=
(a)
Note the angle at the centre of the shaded arc is 360° - 90° = 270°, thus
=
=
( cross- multiply )
3C = 180 ( divide both sides by 3 )
C = 60 mm
(b)
Note the angle at the centre of the shaded arc is 360° - 135° = 225°, thus
=
( cross- multiply )
225C = 1188 ( divide both sides by 225 )
C = 5.28 cm