Firstly, let's fond out now many square metres the decorators are working with
5082/6.60 = 770
Now, the eight = 5.5 so we'll work out the length by 770 / 5.5 = 140
So, four sides of a hall add up to 140, so two add up to 70. The relationship between the sides = 4 : 3, which when applied to 70 gives a length of 40 and a breadth of 30.