Plz tell 27 ??

Dear student,
27. 

 

Let the speed of the streamer =xkm/h 
The speed downstream =(x+5)km/h and 
The speed upstream =(x−5)km/h 
According to the given problem , 
$\frac{90}{x+5}=\frac{60}{x-5}$
On cross multiplication , we get , 
90(x−5)=60(x+5) 
90x−450=60x+300 
90x−60x=300+450 
We get, 
30x=750 
x=750/30​ 
x=25 
Therefore , the speed of the streamer in still water is 25km/h 

Regards