Question

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 areas of four walls. Find the height of the hall.

• A. 8.9 m
• B. 9.1 m
• C. 7.24 m
• D. None of these

Answer 1

The correct option is A 8.9 m

The length of a cinema hall = h m
Length = 20 m and width = 16 m
Area of the floor = Area of the roof = l $\times$ b
= 20 $\times$ 16 = 320 $m^2$
Total area of the floor and roof of the hall = 2 $\times$ 320 = 640 $m^2$
Area of the four walls = 2 (l + b) h
= 2 (20 + 16) $\times$ h
$\Rightarrow$ 640 = 74 $\times$ h
$\Rightarrow$ h = 8.9 m