Question

The central hall of a school is $100m$ long and $15m$ high. It has $10$ doors each of size $4m$ x $2m$ and $10$ windows each of size $1.5m$ x $2m$. If the cost of white washing the walls of the hall at the rate of $Rs.1.40$ per $m^2$ is $Rs.6986$, find the breadth of the hall.

Answer 1

Length of hall, $l=100$ m

Height of hall , $h=15$ m

Let breadth of hall be $b$ m

Then, according to question,

$[2\times 15(100+b)-10\times 4\times 2-10\times 1.5\times 2]\times 1.4=6986$

$\left[30\right(100+b)-80-30]\times 1.4=6986$

$(30b+2890)1.4=6986$

$3b+289=499$

$3b=210$

$b=70$ $m$