Question

In his boat, Sheldon can travel 45 mi downstream in the same time that it takes to travel 9 mi upstream. If the rate of the current is 6 mph, find the rate of the boat in
still water.

Answer 1

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:

$Speed=\frac{Distance}{Time}\\\\\#Upstream\\(u-6)t=9\\\\\#Donwstream\\\\(u+6)t=45$

#Since t is equal in both, we can do away with t.

#We the divide the downstream equation by the upstream equation as:

$\frac{u+6}{u-6}=\frac{45}{9}\\\\(u+6)=5(u-6)\\\\u+6=5u-30\\\\4u=36\\\\u=9$

Hence, the boat's speed in still water is  9 mph