鶴つる亀かめ算ざん

noun

crane-tortoise calculation; solving for two unknowns from totals

A classic Japanese math problem: given the total number of heads and legs of cranes and tortoises, find how many of each. By extension, any problem of solving for two unknowns from their total count and the total of one attribute.

• 鶴つる亀かめ算ざんは、江え戸ど時じ代だいの和わ算さんでよく使つかわれた問もん題だいです。

  The crane-tortoise calculation is a problem often used in Edo-period Japanese mathematics.