Answer:
53.53 km/h
Explanation:
Given that the person drives for 30.0 min at 80.0 km/h, 12.0 min at 105 km/h, and 45.0 min at 40.0 km/h, and he spends 15.0 min eating lunch and buying gas.
So, the total time to complete the journey is
t=30+12+45+15=102 min
hours
As distance=(speed)x(time), so
the distance covered in 30 minutes with a speed of 80 km/h
km.
The distance covered in 12 minutes with a speed of 105 km/h
.
The distance covered in 45 minutes with a speed of 40 km/h
.
So, to the total distance covered is
![d=d_1+d_2+d_3](https://tex.z-dn.net/?f=d%3Dd_1%2Bd_2%2Bd_3)
![=40+21+30=91 km](https://tex.z-dn.net/?f=%3D40%2B21%2B30%3D91%20km)
As the average speed = (Total distance covered)/(Total time taken)
So, the average speed for the whole journey
![=\frac{d}{t}](https://tex.z-dn.net/?f=%3D%5Cfrac%7Bd%7D%7Bt%7D)
.
Hence, the average speed for the trip is 53.53 km/h.