Answer: 3.6 hours
Step-by-step explanation:
Given : The time taken by Blake to paint the room : [tex]t_1=9\text{ hours}[/tex]
The time taken by Ned to paint the room : [tex]t_2=6\text{ hours}[/tex]
Then , the time taken (T) by both of them to paint the room if they work together is given by :-
[tex]\dfrac{1}{T}=\dfrac{1}{t_1}+\dfrac{1}{t_2}\\\\\Rightarrow\ \dfrac{1}{T}=\dfrac{1}{9}+\dfrac{1}{6}\\\\\Rightarrow\dfrac{1}{T}=\dfrac{5}{18}\\\\\Rightarrow\ T=\dfrac{18}{5}=3.6\text{ hours}[/tex]
Hence, it will take 3.6 hours to the two companies if they working together .