To solve this problem we will apply the linear motion kinematic equations. We will start by finding the quantity shifted through the relationship given by the product between speed and time (Time will be converted to hours since the speed is thus specified).
Later, with the given speed we will find the return time.
The general formula of velocity tells us that it is the distance traveled in a certain time, so from it we will obtain the subsequent derivations.
[tex]v = \frac{x}{t} \Rightarrow x = vt \Rightarrow t = \frac{x}{v}[/tex]
Here,
x = Distance
t = Time
Amount of distance traveled for 20 mins
[tex]x = (15\frac{miles}{hour})(20 min \frac{1hour}{60min})[/tex]
[tex]x = 5miles[/tex]
Amount time taken to return back
[tex]t = \frac{x}{v}[/tex]
[tex]t = \frac{5 miles}{10mph}[/tex]
[tex]t = \frac{1}{2} h = 30minutes[/tex]
Total time taken
[tex]T = 20+5+30[/tex]
[tex]T = 55minutes[/tex]
Therefore he takes around of 55 minutes to do that trip.
