Answer:
Step-by-step explanation:
When we measure a given physical quantity then after measurement we give the magnitude as well as unit along with the measurement
Here number gives the magnitude of the measurement what we did and unit gives an idea what unit is for the given measurement we used
Here unit is essential while we did any measurement because unit of the measurement may be different for different group of people but the quantity is always same when we compare them along with the unit
For example we know that

here the numbers are different in two unit system but the quantity we compared is same.
so it is always essential to put units with all measurement to have complete idea of the quantity that is measured