<span>v = 45 km/hr
u = 72 km/hr
Can't sketch the graph, but can describe it.
The Y-axis will be the distance. At the origin it will be 0, and at the highest point it will have the value of 120. The X-axis will be time in minutes. At the origin it will be 0 and at the rightmost point, it will be 160. The graph will consist of 3 line segments. They are
1. A segment from (0,0) to (80,60)
2. A segment from (80,60) to (110,60)
3. A segment from (110,60) to (160,120)
The motorist originally intended on driving for 2 2/3 hours to travel 120 km. So divide the distance by the time to get the original intended speed.
120 km / 8/3 = 120 km * 3/8 = 360/8 = 45 km/hr
After traveling for 80 minutes (half of the original time allowed), the motorist should be half of the way to the destination, or 120/2 = 60km. Let's verify that.
45 * 4/3 = 180/3 = 60 km.
So we have a good cross check that our initial speed was correct. v = 45 km/hr
Now having spent 30 minutes fixing the problem, out motorist now has 160-80-30 = 50 minutes available to travel 60 km. So let's divide the distance by time:
60 / 5/6 = 60 * 6/5 = 360/5 = 72 km/hr
So the 2nd leg of the trip was at a speed of 72 km/hr</span>
