MDU RESOURCES GROUP, INC. COMPUTATION OF RATIO OF EARNINGS TO FIXED CHARGES AND COMBINED FIXED CHARGES AND PREFERRED STOCK DIVIDENDS Twelve Months Year Ended Ended March 31, 2003 December 31, 2002 (In thousands of dollars) Earnings Available for Fixed Charges: Net Income per Consolidated Statements of Income $ 144,830 $ 148,444 Income Taxes (a) 82,365 86,230 227,195 234,674 Rents (b) 8,272 8,156 Interest (c) 53,504 51,393 Total Earnings Available for Fixed Charges $ 288,971 $ 294,223 Preferred Dividend Requirements $ 755 $ 756 Ratio of Income Before Income Taxes to Net Income 157% 158% Preferred Dividend Factor on Pretax Basis 1,185 1,194 Fixed Charges (d) 61,776 59,549 Combined Fixed Charges and Preferred Stock Dividends $ 62,961 $ 60,743 Ratio of Earnings to Fixed Charges 4.7x 4.9x Ratio of Earnings to Combined Fixed Charges and Preferred Stock Dividends 4.6x 4.8x (a) Includes income tax benefits of $4,821 associated with the cumulative effect of accounting change for the twelve months ended March 31, 2003. (b) Represents portion (33 1/3%) of rents which is estimated to approximately constitute the return to the lessors on their investment in leased premises. (c) 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. (d) Represents rents and interest, both as defined above.