Question

A classroom is $7m$ long, $6m$ broad and $4m$ high. The doors and windows occupy an area of $7m^2$. Find the cost of whitewashing the walls and roof at the rate of $Rs.15per{m}^2$.

Answer 1

TSA of the room = $2(lb+bh+hl)$ - area of the floor

$=2(lb+bh+hl)-lb$

$=lb+2(bh+hl)$

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

$=7\times 6+2\times 4(7+6)$

$=42+8\left(13\right)$

$=42+104=146m^2$

where

l=7m

b=6m

h=4m

cost of white washing per $m^2$ = Rs 15

cost of white washing 146 $m^2=146\times 15$

= Rs 2,190