Question

The length of a cinema hall is $20m$ and breadth is $16m.$ 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. 7.5 m

Answer 1

The correct option is A 8.9 m

Let the Height of a cinema hall be ${}^{\prime }{h}^{\prime }$

Length $=20m$ and width $=16m$

Area of the floor $=$ Area of the roof $=l\times b$

$=20\times 16=320m^2$

Total area of the floor and roof of the hall $=2\times 320=640m^2$

Area of the four walls $=2(l+b)h$

$=2(20+16)\times h$

$=2\times 36\times h$

$=72\times h$

It is given that the sum of areas of floor and flat roof $=$ Area of four walls

$\therefore 640=72\times h$

$\Rightarrow h=\frac{640}{72}=8.9m$