Distance = Speed × Time.

• Distance jogged = 4 km/h × \( \frac{1}{4} \) h = 1 km
• Time at 3 km/h = Distance ÷ Speed = 1 km ÷ 3 km/h = \( \frac{1}{3} \) h
• \( \frac{1}{3} \) h = 20 minutes

Final Answer: \( \frac{1}{3} \) h