If the board determines that the petition is signed by owners representing at least 60 percent of the total assessed valuation of the real property within the proposed zone as shown by the last equalized assessment roll of the county, or by at least 60 percent of the taxpayers resident within the proposed zone, as its boundaries shall have been established upon the hearing on the petition, the board may by resolution reciting the finding declare that an election is unnecessary and that the zone is established.