A dog start chasing to a cat 2 hour later. It takes 2 hours to dog to catch the cat. If the speed of the dog is 30 km/h. what is the speed of cat?

Explanation:-

Let speed of the cat be S km/h.
Time taken = Distanced advanced / relative speed
2 = ^{2 * S}/_(30-S)
S = 15 km/h.