SDCL § 47-23-20: Quorum of directors--Provisions of articles or bylaws as governing.

A majority of the number of directors fixed by the bylaws, or in the absence of a bylaw fixing the number of directors, then of the number stated in the articles of incorporation, shall constitute a quorum for the transaction of business, unless otherwise provided in the articles of incorporation or the bylaws; but in no event shall a quorum consist of less than one-third of the number of directors so fixed or stated. The act of the majority of the directors present at a meeting at which a quorum is present shall be the act of the board of directors, unless the act of a greater number is required by chapters 47-22 to 47-28, inclusive, the articles of incorporation or the bylaws.