Explanation:
A)
If we look at the graph at 10 mins its evident that there has been some movement meaning Joes has moved 1km (as we can see in the graph) away from the starting point.
B)
For the last 30 mins of the graph we can see some changes.
so Joe started at 30 mins and ended at 60mins so there is a difference of 30 mins. In those 30 mins Joe moved from 0km to 4km. Meaning that Joe moved at 4km in 30 mins.
We are going to work this out in KPH. Since we have 30 mins and the unit we are using to measure his speed is measured in hours, we need to double it along with the kilometres he moved so it stays fair and constant. so we will have 8km and 60 min (1 hour). Therefore Joe moved at 8kph.
Hope this helps