only child inheritance

Question

An only son inherited a 3/4 hectare lot. He decided to build a 40-door condominium on the lot. The floor are of the units is uniform and the total floor area of the entire condominium is 1/5 less than the area of the lot to provide for certain amenities. What is the floor area of each condominium unit?

Answer 1

1 hectare = 10,000m²

0.75 hectare = 7,500m²

1/5 less means 4/5 present

4/5 of 7,500m² = 6,000m²