First let do the whole area 100*75 = 7500 m²
Now let's calculate the area of the Arena Diameter (A=πr²)of 50 m .
A = 3.14*25 (half the diameter of 50) = 78.5 m² and now only half if overlapping, thus divide by 2 = 39.25 m²
Now we should be able to deduct 7500 m² - 39.25 m² = 7460.75 m²
