Inch is one of the units of measuring length.
Converting from inch to meters,
A 12-inch ruler converted to meters will be;
Converting the meter equivalent of the ruler into the sub-units of meters measurement,
![\begin{gathered} 0.3048m \\ To\text{ kilometer} \\ 1000m=1\operatorname{km} \\ 0.3048m=(0.3048)/(1000)=0.0003048\operatorname{km} \\ \\ To\text{ millimeter} \\ 1m=1000\operatorname{mm} \\ 0.3048m=0.3048*1000=304.8\operatorname{mm} \\ \\ \\ To\text{ centimeters} \\ \text{1m =100cm} \\ 0.3048m\text{ =0.3048}*100=30.48\operatorname{cm} \\ \\ \\ To\text{ meters } \\ 12\text{ inch = 0.3048m} \end{gathered}]()
From the conversions of metric units of length above, the 12-inch ruler measures 30.48cm which is closest to 30cm
Therefore, the ruler is closest to 30 centimeters