Inch is one of the units of measuring length.
Converting from inch to meters,
[tex]1inch=0.0254m[/tex]A 12-inch ruler converted to meters will be;
[tex]12\times0.0254=0.3048m[/tex]Converting the meter equivalent of the ruler into the sub-units of meters measurement,
[tex]\begin{gathered} 0.3048m \\ To\text{ kilometer} \\ 1000m=1\operatorname{km} \\ 0.3048m=\frac{0.3048}{1000}=0.0003048\operatorname{km} \\ \\ To\text{ millimeter} \\ 1m=1000\operatorname{mm} \\ 0.3048m=0.3048\times1000=304.8\operatorname{mm} \\ \\ \\ To\text{ centimeters} \\ \text{1m =100cm} \\ 0.3048m\text{ =0.3048}\times100=30.48\operatorname{cm} \\ \\ \\ To\text{ meters } \\ 12\text{ inch = 0.3048m} \end{gathered}[/tex]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