Two bikers simultaneously started towards each other from two cities that are 232 km apart. they met 8 hours later. what was the speed of the second biker if the first one was travelling at a speed of 13 km/h?

First we need to determine how far the first biker was able to go. 

This means that the first biker was able to travel 104km, so now we need to find out how far the second biker was able to go. Becasue they both had to meet, we need to subtract the first bikers distance from the total distance between the cities. 

Meaning that the distance that the second biker traveled 128km.  
Because  we just need to plug the second bikers stats into the equation to find out their speed. 

2r*3.14
(the diameter is the same thing as 2r)
14*3.14
43.96