In a computer game, a builder can build a wall in ten hours while a destroyer can demolish such a wall completely in fourteen hours. Both, the builder and the destroyer were initially set to work together on level ground. But after 7 hours the destroyer was taken out. What was the total time (in hrs) taken to build the wall ?
Mooring buoy are white with a blue horizontal band. They usually are placed in marinas and other areas where boats are allowed to anchor. These are the only buoys you may tie up to legally.