Assume that the population of the least populated district = n

Since we know that the difference should be no more than 10 % that means following

Least Populated District = n
Next District in ascending order of population = 1.1 n

Now "n" will be the lowest number ONLY IF all the remaining 10 districts have the same population of 1.1n. Hence

n + 10*(1.1*n)) = 132,000
n + 11n = 132,000
12n = 132,000
n = 11,000

This is my answer choice.