How many metres of a carpet $75$ cm wide will be required to cover the floor of a room which is $20$ metres long and $12$ metres broad?

The correct option is B $320$ m
Given ,

For room , length $=20m$ and breadth $=12m$

Area of room $=20\times 12=240m^2-\left(1\right)$
$75cm=0.75m$

Let $l$ be the length of carpet

Area of carpet required=$l\times 0.75m^2-\left(2\right)$

From eqs.(1) and (2)

$\therefore l\times 0.75=240\to l=\frac{240}{0.75}=320m$