Exhibit 12 MDU RESOURCES GROUP, INC. COMPUTATION OF RATIO OF EARNINGS TO COMBINED FIXED CHARGES AND PREFERRED DIVIDENDS Twelve Months Year Ended Ended June 30, 1997 December 31, 1996 (In thousands of dollars) Earnings Available for Fixed Charges: Net Income per Consolidated Statements of Income $ 47,074 $45,470 Income Taxes 16,384 16,087 63,458 61,557 Rents (a) 1,032 1,031 Interest (b) 33,621 34,101 Total Earnings Available for Fixed Charges $ 98,111 $96,689 Preferred Dividend Requirements $ 784 $ 787 Ratio of Income Before Income Taxes to Net Income 135% 135% Preferred Dividend Factor on Pretax Basis 1,058 1,062 Fixed Charges (c) 34,653 35,132 $ 35,711 $36,194 Ratio of Earnings to Combined Fixed Charges and Preferred Dividends 2.75x 2.67x (a) Represents portion (33 1/3%) of rents which is estimated to approximately constitute the return to the lessors on their investment in leased premises. (b) Represents interest and amortization of debt discount and expense on all indebtedness and excludes amortization of gains or losses on reacquired debt which, under the Uniform System of Accounts, is classified as a reduction of, or increase in, interest expense in the Consolidated Statements of Income. Also includes carrying costs associated with natural gas available under a repurchase agreement with Frontier Gas Storage Company as more fully described in Notes to Consolidated Financial Statements. (c) Represents rents and interest, both as defined above.