二一添作五

Explanation: This is a division of an abacus formulas, is half the mean equal to 0.5. Metaphor both sides equally. 　　Source: Qing Shi Yukun "San Xia Wu Yi," the second time choose to take the 'add 21 to 5' of belongings, and now we have to face '31 31' a. " 　　Examples: S the deal, regardless of Profits, ~. Thesaurus:  half-and-half