minimum pop for least populated would be 1 village with exacly 10% less than all the rest.
backsolve.
B) 10.800 + 10% = 11.880
11.880*10+10.800 = 118.800+10.800 = 129.600, not the same total, wrong

D)11.000 + 10% = 12.100
12.100*10+11.000 = 121.000+11.000 = 132.000, same as total, D is the answer

in backsolving there are many strategies, i always try (if the result sets are ordered, which they usually are) first B, if the result is larger than expected A is the answer (always confirm), if the result is less than expected try D, aplly the same reasoning untill you find the answer.

another method would be to assume the county with the minimum popolation is X

and all other are 10% more than X.

So X + 4( 1.1X) = 132000

so 12X =132000
X = 11000

"So X + 4( 1.1X) = 132000

so 12X =132000 "
I believe you mean
So X + 10( 1.1X) = 132000
so 12X =132000

good way to solve it by the way. 8)

yup, it 10 not 4, thanks for correcting that