Fuzzy calculus with aplications

The aim of the artile is presenting the current state of ordered fuzzy numbers development. New model of fuzzy number was invented in 2002 to overcome drawbacks of classical (convex) fuzzy numbers. Two problems of management accounting are considered. The first relates to the management of supply and determining the optimal size of a delivery from outside, which minimalize total costs, when unit costs of delivery and storage are fuzzy. The second problem is related to determination of Internal Rate of Return (IRR) for investments in which the value of cash flow are not specified accurately. Key words and phrases: ordered fuzzy numbers, partial order relations, defuzzification functionals, management of supply, net present value (NPV), internal rate of return (IRR).