Children = \( \frac{9}{10} \) of all people.
Girls = \( \frac{2}{3} \) of children (Boys : Girls = 1 : 2).

• Girls = \( \frac{2}{3} \times \frac{9}{10} = \frac{18}{30} = \frac{3}{5} \)
• = 0.6 × 100% = 60%

Final Answer: 60%