Home›Browse›mental abacus🌐EnglishEnglishItalianoРусский中文EntityQ10419540· pop 5· linked from 11 articlesmental abacusSign in to saveAlso known as abacus systemsystem where users mentally visualize an abacus to do calculationsAvailable in 5 languages中文РусскийGreeksimplevia Wikidata sitelinks · CC0