The Japan Academy

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Vol. 79 No. 1 (2003)

Vol. 79 No. 1 (2003)

Calculation of Mouse Reproduction Potential (Nezumi-zan and Geometric Progression)

  This illustration is taken from the elementary mathematical textbook “Jinkoki” by Mitsuyoshi Yoshida, a Japanese mathematician who lived in the 17th century during the Edo era. From this figure, we can calculate the total number of mice produced by geometric progression in one mouse family over a period of one year. Suppose that a pair of mice breeds and 12 baby mice are born in January. In the next month, the pair and their 12 baby mice (6 pairs) also reproduced with litters of 12 baby mice. The total number of mice in the family is then 98 (14 + 7×12) in February. If each pair breeds 12 baby mice every month for the remainder of the year, the total number of animals would be 27,682,574,402 (2×712) in December.