Answer:
r = 4.2 cm; d = 8.4 cm
Step-by-step explanation:
The radius is the distance from the centre of the circle to the circumference.
r = 4.2 cm
The diameter is the length of a straight line that passes through the centre with each end at the circumference.
d = 2r = 2 × 4.2 cm = 8.4 cm
