There is a hill behind a person’s house. He walks up the top of the hill at a speed of 1$\frac{1}{2}$ km/hour, but walks down it at 4 $\frac{1}{2}$ km/ hour. If it takes him 6 hours for the entire journey, the distance, in km, from his house to the top of the hill is
There is a hill behind a person’s house. He walks up the top of the hill at a speed of 1$\frac{1}{2}$ km/hour, but walks down it at 4 $\frac{1}{2}$ km/ hour. If it takes him 6 hours for the entire journey, the distance, in km, from his house to the top of the hill is