Answer:
9 Km/h
Step-by-step explanation:
Walking 3 Km for 20 minutes from the definition of speed, it's distance covered per unit time. Here, the distance covered is expressed per unit hour.

Substituting 3.5 Km for distance and time for 20 minutes
To convert time into hours, we divide the minutes by 60 hence time=20/60=1/3 hours

Therefore, the speed is 9 Km/h
Answer:
1. What happens when air is heated or cooled? ... So air, like most other substances, expands when heated and contracts when cooled. Because there is more space between the molecules, the air is less dense than the surrounding matter and the hot air floats upward.
Step-by-step explanation:
Hope this helps