You would observe the length of objects.
None. A metric ruler would not show inches, as these are not a metric measurements. It would show millimetres and centimetres.
To measure the mm of an item you would need to use a metric ruler. The metric ruler has cm and mm on it.
Metric ruler
A metric ruler measures in inches and centimeters.
A ruler
A small ruler such as one used in an office or school would be set out in Millimetres and Centimetres.
0.03125 = 1/32 inches.
A ruler.
A metric ruler.
You would use a ruler and measure in millimeters or centimeters.
a balance and a metric ruler.
ruler * * * * * A ruler is not a unit! Most people would use centimetres, though retailers may use millimetres.