MDU RESOURCES GROUP, INC. COMPUTATION OF RATIO OF EARNINGS TO FIXED CHARGES AND COMBINED FIXED CHARGES AND PREFERRED STOCK DIVIDENDS Years Ended December 31, 1997 1996 1995 1994 1993 (In thousands of dollars) Earnings Available for Fixed Charges: Net Income per Consolidated Statements of Income $ 54,617 $ 45,470 $ 41,633 $ 39,845 $ 38,817* Income Taxes 30,743 16,087 23,057 18,833 19,982* 85,360 61,557 64,690 58,678 58,799 Rents (a) 1,249 1,031 894 878 871 Interest (b) 33,047 34,101 29,924 29,173 27,928 Total Earnings Available for Fixed Charges $119,656 $ 96,689 $ 95,508 $ 88,729 $ 87,598* Preferred Dividend Requirements $ 782 $ 787 $ 792 $ 797 $ 802 Ratio of Income Before Income Taxes to Net Income 156% 135% 155% 147% 151% Preferred Dividend Factor on Pretax Basis 1,220 1,062 1,228 1,172 1,211 Fixed Charges (c) 34,296 35,132 30,818 30,051 28,799 Combined Fixed Charges and Preferred Stock Dividends $ 35,516 $ 36,194 $ 32,046 $ 31,223 $ 30,010 Ratio of Earnings to Fixed Charges 3.49x 2.75x 3.10x 2.95x 3.04x* Ratio of Earnings to Combined Fixed Charges and Preferred Stock Dividends 3.37x 2.67x 2.98x 2.84x 2.92x* * Before cumulative effect of accounting change of $5,521 (net of income taxes). (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.