Sarah wants to find out how long it will take her to walk from her house to her friend's house. On the map, it shows that Sarah's house is 4 cm from her friend's house. The ratio scale of the map is 1:50000. On average, it will take Sarah 10 mins to walk 1km. How long will it take Sarah to walk to her friend's house?
First, we need to convert the distance on the map to actual distance in kilometers.
Since the ratio scale is 1:50000, 1 cm on the map represents 50000 cm in real life. Therefore, 4 cm on the map represents 4 * 50000 = 200000 cm in real life.
Converting 200000 cm to km, we get 2 km.
Given that Sarah takes 10 mins to walk 1 km, she will take 10 * 2 = 20 mins to walk 2 km.
Therefore, it will take Sarah 20 mins to walk to her friend's house.