Each petition shall be signed by a number of qualified electors equal to the lesser of (1) one per cent of the votes cast for the same office or offices at the last-preceding election, or the number of qualified electors prescribed by § 9-380 with regard to newly-created offices, or (2) seven thousand five hundred. “Qualified electors” means electors eligible to vote for all the candidates proposed by the petition. “Votes cast for the same office at the last-preceding election” means, in the case of multiple openings for the same office, the total number of electors checked as having voted at the last-preceding election at which such office appeared on the ballot.