We drove our Car in rural Konkan area recently. Distance was about 160 miles. Roads were good and bad in patches. On good patches, we enjoyed driving at speed of 60 miles per hour. Whereas, on bad patches, it was difficult to go beyond 10 miles per hour. A general feeling was that we were at the slower speed for about 4 hours and at the higher speed for only 2 hours. Roads were bad; that was the conclusion. You can understand that about two-third of the travel time, we were struggling to get a speed of 10 miles per hour.
Let us see another aspect of the journey by getting idea about length of the bad or good road. Since, we had 4 hours of drive at a speed of 10 miles per hour, the length of such roads was 10*4 = 40 miles. Similarly, length of the road travelled in 2 hours at 60 miles per hour can be computed as 60*2 = 120 miles. So, total distance travelled was 120+40 = 160 miles, out of which 120 miles were good and only 40 miles were rough. In terms of %, only (40/160)*100 = 25% of the roads were bad whereas 75% of the roads were in good condition.
It's interesting to observe that from officials’ point of view who maintain the roads, three-fourth of the roads are nicely maintained but from travellers’ point of view, they must spend two-third of their travel time on bad roads.
This example is useful in experimenting with the data related to speed, distance, and proportion of good/bad roads. It helps in understanding the concept of speed, distance, percent, average etc. in interesting way.