The words to appear upon the ballots shall be “Bonds—Yes” and “Bonds—No,” or words of similar import. A brief statement of the proposition, setting forth the amount of the bonds to be voted upon, the maximum rate of interest, and the purposes for which the proceeds of the sale of the bonds are to be used, shall be printed upon the ballot. No defect in the statement other than in the statement of the amount of the bonds to be authorized shall invalidate the bonds election.