For the purpose of ascertaining the number of inhabitants in the several districts provided by section 23-204, the supervisors or commissioners, as the case may be, shall ascertain the whole number of votes cast at the last preceding general election held within the county, and shall multiply the number of votes so cast by five. This result shall be taken as the whole number of inhabitants of the county or any part thereof as the case may be, and the supervisor districts shall be divided upon the foregoing basis and in accordance with the results thus obtained.