Question

The length of a hall is $18m$ and the width $12m$. 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 in m.

Answer 1

Let the height of the hall be $h$ metres

We have, $l=18m$ and $b=12m$

Now,

Sum of the areas of the floor and roof $=$ Sum of the areas of four walls

$\Rightarrow 2lb=2(l+b)h$

$\Rightarrow lb=(l+b)h$

$\Rightarrow h=\frac{lb}{l+b}=\frac{18\times 12}{18+12}=7.2m$