Question 1
Al lives in Alton and Ben lives 12 km away in Benburg. They want to go to Centreville which is 30 km from Alton and 20 km from Benburg. Ben asks Al to take a taxi from Alton to Benburg to pick him up so they can go to Centreville together. The cost of the taxi is 1000 rupiahs per km. Ben pays the part of the fare resulting from the extra distance caused by this detour, and shares equally the remaining cost with Al. How much does Ben save from sharing the taxi fare with Al?