Question 728440
First, add both rates of the runners
80+90=170
Then, count the number of rates(this number is very important for the next step).
There are 2. 
Now, divide 170 by 2. Dividing the combined rates (170) by the total numbers of rates(2), we will find the average. 
170/2=85 kilos per hour.
Thus, the average kph is 85 kph.