The length of a cinema hall is 20 m and breadth is 16 m. The sum of the areas of floor and flat roof is equal to the area of four walls. Find the height and volume of the hall.

Let the height of the cinema hall = h m 
length = 20 m and width = 16 m
Area of the floor = Area of the roof= l x b
                       = 20 x 16= 320 m²
Total area of the floor and the roof of the hall = 2 x 320 = 640 m²
Area of the four walls = 2( l + b) x h = 2(20 + 16) x h 
                               = 72 h m²
Area of the four walls = Total area of the floor and the roof. 
                   Þ     72 h = 640 
                             Þ h = 8.9 m.
∴volume = l x b x h = 20 x 16 x 8.9 = 2848 m³