A room 4.9 m long and 35 m broad is covered with carpet, leaving an uncovered margin of 25 cm all around the room. If the breadth of the carpet is 80 cm, find its cost at RS 80 per meter.

Length of room = 4.9 m
Breadth of room = 3.5 m
Margin = 25 cm = 0.25 m
Breadth of carpet = 80 cm = 0.8 m
Cost = RS 80 per meter
Now,
Length to be carpeted $=4.9m-(0.25+0.25)m=4.4m$
Breadth to be carpeted $=3.5m-(0.25+0.25)m=3m$
Therefore,
Area to be carpeted $=$ Length to be carpeted $\times$ Breadth to be carpeted
$=4.4\times 3$
$=13.2m^2$
Area of carpet $=$ Area to be carpeted $=13.2m^2$
Now,
Lengthof carpet $=$ $\frac{\text{(area of carpet)}}{\text{(breadth of carpet)}}$= $\frac{13.2}{0.8}$ = $16.5$
Length of carpet is 16.5 m
Now,
Cost of 1 m carpet = RS 80
Therefore,
Cost of 16.5 m carpet $=Rs80\times 16.5m=Rs1,320$