As the first step, let us say that the velocity of the boat in relation to a fixed point in the map of this travel is equal to its velocity in relation to the water PLUS the water velocity in relation to the fixed point WHEN it is in the same direction (travel downstream), and MINUS when traveling in the opposite direction (upstream).
From this, we will remember the definition of velocity by:
[tex]V=\frac{\Delta S}{\Delta t}[/tex]
The ΔS is the distance ran by the boat, which is 60 miles. Δt is 4h for the upstream case, and 3h for the downstream case.
From this, we say that the value of V is for the boat in relation to the water (which is what we need here) and v for the water. Now, we have the following system of equations.
[tex]\begin{gathered} V-v=\frac{60}{4}=15 \\ V+v=\frac{60}{3}=20 \\ \\ V-v=15 \\ V+v=20 \end{gathered}[/tex]
Now, to proceed with the solution, we will sum up the equations, which will result in the following:
[tex]\begin{gathered} V-v+(V+v)=15+20 \\ 2V=35 \\ V=\frac{35}{2} \\ \\ V=17.5mph \end{gathered}[/tex]
From the solution developed above, we are able to conclude that the rate of the boat in still water, what is the velocity the boat reaches in relation to the water, is equal to 17.5 miles per hour.
