Wannan fasaha an san shi da hanyar ƙarewa, kuma ya yi amfani da shi don ƙaddamar da ƙimar π. A cikin ma'auni na Circle ya yi wannan ta hanyar zana babban hexagon na yau da kullum a waje da kuma ƙananan hexagon na yau da kullum a cikin da'irar, kuma a hankali ya ninka adadin bangarori na kowane polygon na yau da kullum, ƙididdige tsawon tsawon kowane bangare na kowane polygon a kowane mataki. Yayin da yawan bangarori ya karu, ya zama mafi kusantar kusanci da lambobi huɗu na ainihi. Bayan tabbatar da irin wannan rikice-rikice (reductio ad absurdum), ya iya ba da amsoshin matsaloli zuwa digiri na daidaituwa, yayin da ya ƙayyade iyakokin da amsar ta kasance. Wannan fasaha an san shi da hanyar ƙarewa, kuma ya yi amfani da shi don ƙaddamar da darajar π. A cikin Ma'aunin Da'irar ya yi wannan ta hanyar zana babban hexagon na yau da kullum a waje da kewaye da ƙananan hexagon na yau da kullum a cikin da'irar, kuma a hankali ya ninka adadin bangarorin kowane polygon na yau
πr2