Our sages teach us that if a person uses 1/10th of an ephah of flour while baking, the person needs to “take challah” [Mishnah Challah 2:6]. Rashi tells us that one ephah equals three se’ah. One se’ah equals six kavim. One kav equals four lugim. One lug equals the volume of six eggs [Rashi on Shemos 16:36]. The volume of an egg is called a beitzah. How many beitzim of flour must there be for the person to have to “take challah”?
3 x 6 x 4 x 6 = 432 -> the number of eggs in one ephah
432/ 10 = 43.2 ephah needed before you take challah