Answer :
We have the following rule for the division of fractions:'
[tex]\begin{gathered} \frac{a}{b}\frac{\cdot}{\cdot}\frac{c}{d}=\frac{a\cdot d}{b\cdot c} \\ b,d\ne0 \end{gathered}[/tex]then, in this case, we have to divide 1/3 by 3/5 to find out how much of the chair will be finished:
[tex]\frac{1}{3}\frac{\cdot}{\cdot}\frac{3}{5}=\frac{1\cdot5}{3\cdot3}=\frac{5}{9}[/tex]thus, after 1/3 hour, only 5/9 of the chair will be finished