___________ have multi-storeyed buildings, too many vehicles, heavily burdened water supply and sewage system.
Big cities
Villages
Small towns
Remote areas
Big cities have multi-storeyed buildings, too many vehicles, heavily burdened water supply and sewage system.
The angles of depression of the top and the bottom of a 10 m tall building from the top of a multi-storeyed building are 30∘ and 45∘, respectively. Find the height of the multi-storeyed building.