If we assume the pit house is a perfect circle, its total area would be
A = pi*(r**2) = pi*(4**2) = 50,265 m2
If we divide the area by the number of adults, we get that each person used
an area of approximately 50,265/10 = 5,02 m2 of area per person
With a Diameter of 12m, the new area would be A = pi*((12/2)**2) = 113,1 m2
If we use the previous estimate of area occupied by a single person, we get that 113,1 / 5,02 = 22,529.
So, an estimate of 22 people would be living now in the pit house.
(Note, that if we use 4m2 as the space it takes to house 1 person inside the house, we would have 113,1/4 = 28,275.
So 28 people would live there)