Speed is defined as the ratio of distance and time. The total distance covered in the journey is 630 kilometers.
Given information:
David drove the first six hours of his journey at 65 km/ hour and the last 3 hours of his journey at 80 km/hour.
Now, the distance covered by David in first 6 hours will be,
[tex]d_1=65\times 6\\d_1=390[/tex]
So, the distance covered in first 6 hours is 390 km.
The distance covered by David in next 3 hours will be,
[tex]d_2=80\times 3\\d_2=240[/tex]
So, the distance covered by David in next 3 hours is 240 km.
The total distance covered in the journey can be calculated as.
[tex]d=d_1+d_2\\d=390+240\\d=630[/tex]
Therefore, the total distance covered in the journey is 630 kilometers.
For more details, refer to the link:
https://brainly.com/question/18909081
