In ancient times there was one great kingdom on whose throne was a just but cruel king named Physicus. King Physicus had his subjects. There were a total of ten subjects. At the end of each year, each of them brought the king ten bars of gold. Each gold bar weighed one kilogram. So, each subject had to hand over ten kilograms of gold to the king. The king's spy informed King Physicus that one subject was making a hundred grams lighter bar, but that they looked the same in size, the only difference was in the density of the gold. King Physicus was a wise man and with one measurement on the scales he found out which subject was stealing from him. The question is: how did King Physicus find out who the thief was with just one measurement?