Answer:
9 mph
Step-by-step explanation:
-let x be the speed of current and t be time. The speed equation for both directions can then be represented as:
[tex]Speed=\frac{Distance}{Time}\\\\\#Upstream\\(u-6)t=9\\\\\#Donwstream\\\\(u+6)t=45[/tex]
#Since t is equal in both, we can do away with t.
#We the divide the downstream equation by the upstream equation as:
[tex]\frac{u+6}{u-6}=\frac{45}{9}\\\\(u+6)=5(u-6)\\\\u+6=5u-30\\\\4u=36\\\\u=9[/tex]
Hence, the boat's speed in still water is 9 mph
