Two twins are running away from their mother in opposite directions one with the speed of 10 feet per second and the other with the speed of 8 feet per second. How and with what speed does the distance between the twins change?

Identify all the cases where non-probability sampling is used when attempting to study the characteristics of a large city. studies on every subject in the population divide a population in groups and obtain a sample studies with a limited amount of time demonstrate existing traits in a population studies with the nth person selected