First, consider the formula for area of a circle:
Area of a circle= π r²
Secondly, because the diameter is double the radius, and we have been given the diameter, we can find the radius!
d/2=r
(240mm) / 2= r
120mm = r
Finally, now that we know the radius, we can find the area!
Area = π r²
= π (120)²
= π 14400mm² OR 45238.93 mm²
Hope this helps!