The length of a hall is 18 m and the width 12 m. The sum of the areas of the floor and the flat roof is equal to the sum of the areas of the four walls. Find the height of the hall.
Given,
Length of a hall = 18 m
Width of hall = 12 m
Sum of area of floor and area of roof = sum of area of four walls
Let height of hall = h m
= l×b+l×b = 2(l+b)h
= 2lb = 2(l+b)h = h = 
8