The metric system is based upon multiples of ten. The metre is divided into 100 equal parts. One hundredth part of a metre is called a centimetre (cm).
So a hundred centimetres make one metre. Again a centimetre is divided into ten equal parts called millimetres (mm). 10 millimetres make 1 centimetre, 100 centimetres make 1 metre.
Now let’s look at a section of the rule between 4 cm and 5 cm.
There are 10 equal divisions which are equal to 1/10 cm or 1 mm. To measure 44 mm, first locate the longest line designated 4 cm or 40 mm. Next count 4 additional lines to find 44 mm.