To solve \( \frac{3}{10} \div \frac{1}{3} \), you can multiply by the reciprocal of \( \frac{1}{3} \):
\[ \frac{3}{10} \div \frac{1}{3} = \frac{3}{10} \times \frac{3}{1} \]
Now multiply the fractions:
\[ \frac{3 \times 3}{10 \times 1} = \frac{9}{10} \]
So, the answer is:
\[ \frac{9}{10} \]