When we write length as 3.2 cm, it means that the measurement has only 2 significant figures and the length has been measured by measuring instrument having a least count if 0.1 cm. However, when we write the length as 3.200 cm, it means that the measurement has 4 significant figures i.e, the measurement has been done using an instrument having a least count of 0.001 cm. Thus, the second measurement is more precise.