There are 12 dogs at the dog park on a busy Saturday. 3 of them are golden retrievers. What is the probability that a randomly selected dog is a golden retriever?

This size running track is usually called a 400 meter track. however if a person ran as close to the inside as possible on the track they would run less than 400 meters in one lap. how far away from the inside border would someone have to run to make one lap equal exactly 400 meters