Observe the ruler, it is marked in centimeters. \

The long marks are centimeters, and the shorter marks are millimeters and there are 10 millimeters (mm) for each centimeter (cm).

The object starts at 0^th short mark and ends at 13^th short mark.

Length of object = 13 millimeters.

= 10 mm + 3 mm                             (Rewrite 13 as 10 + 3)

= 1 cm + 0.3 cm                               (10 millimeters = 1 centimeter)

= 1.3 cm

The length of the object is 1.3 cm.