This paper is to follow the previous part 5 and 6. In part 5 the experimental results and the fiber properties which effectively work as the dispersed phase in inorganic matrices are explained and the foundermental fiber reinforcing mechanism on inorganic matrices under the tensile stress is indicated. In part 6 a model explaining the tensile fracture mechanism of fiber reinforced inorganic composite materials is suggested and on the basis of this model the theoretical tensile strength of fiber reinforced inorganic composite materials is proposed. In this paper the theoretical ultimate tensile strengths of steel fiber reinforced cement mortar and glass fiber reinforced Gypsum are analysed and compared with experimental values. The experimental results support the theoretical analyses on the ultimate tensile strengths of fiber reinforced inorganic composite materials as follows. There are certain limited values on the fiber volume ratio and the fiber aspect atio (=l/d). When the fiber volume ratio and the fiber aspect ratio are smaller than these limited values, the ultimate tensile strength of fiber reinforced inorganic composite materials is similar to the tensile strength of the matrix. Only when the fiber volume ratio and the fiber aspect ratio are bigger than those limited values, the fiber reinforcement works effectively and it is possible to decrease the limited value of the fiber volume ratio by increasing the fiber aspect ratio.