If you divide a meter stick into 3 equal parts, they are “approximately” equal. If you measure very, cery carefully, and use a very thin razor to make the mark, you may be able to to get accuracy to the 3rd and maybe the 4th decimal place, but then you will start running into problems with dividing mark thickness, and ability to measure so accurately. So, dividing into 3 equal parts is an excercise in making careful approximation, and not 100% exact equal parts.