[tex] \huge\hookrightarrow \mathbb{ \color{gold}Answer}[/tex]
We know,
[tex] \boxed{volume = l \times b \times h}[/tex]
so,
[tex]\hookrightarrow{volume = 6 \times 4 \times 9}[/tex]
[tex]\hookrightarrow volume = 216 \: m {}^{3} [/tex]
now,
[tex] \boxed{density = \frac{mass}{volume} }[/tex]
So,
[tex] \hookrightarrow1.3 = \dfrac{m}{216} [/tex]
[tex]\hookrightarrow \: m = 216 \times 1.3[/tex]
[tex] \hookrightarrow \: m = 280.8[/tex]
hence, mass of air in the room is 280.8 kg
