Following chromatogram was developed by adsorption of compound ' A ' on a 6 cm TLC glass plate.…

From the above picture of chromatographic plate, retardation factor is:
${\mathrm{R}}_{\mathrm{f}}=\frac{\text{ Distance moved by the substance from base line }}{\text{ Distance moved by the solvent from base line }}$

$=\frac{3.0 \mathrm{cm}}{5.0 \mathrm{cm}}=0.6$ or $6\times {10}^{-1}$.