Answer:
The average speed of the car is [tex]s = 24\ mph[/tex]
Step-by-step explanation:
The average speed is defined as
[tex]s = \frac{d_1}{t}[/tex]
Where
s is the speed
d is the displacement made
t is the time it took to perform the displacement d.
On the first trip the speed was 20 mph and the displacement was 60 miles. Then we find the time [tex]t_1[/tex]
[tex]s = \frac{d}{t}[/tex]
[tex]t_1 = \frac{d_1}{s}\\\\t_1 = \frac{60}{20}\\\\t_1 = 3\ h[/tex]
On the second trip the speed was 30 mph and the distance traveled was the same: 60mph
We calculate [tex]t_2[/tex].
[tex]t_2 = \frac{60}{30}\\\\t_2 = 2\ h[/tex].
Now we can calculate the average speed for the entire route
[tex]s = \frac{d_1 + d_2}{t_1 + t_2}\\\\s = 60 +\frac{60}{3} +2\\\\s = \frac{120}{4}\\\\s = 24\ mph[/tex]
