9
an express train makes a run of 240 km at a certain speed. another train whose
speed is 12 km/hr less takes an hour longer to cover the same distance. find the
speed of the express train in km/hr.
the titlur

Using complete sentences, describe the central economic problem facing all humans. why does this require people to make choices? how can this result in opportunity costs?

Use your vocabulary words to complete the sentences below. more of the world's population is now concentrated in heavily populated urban areas known as a this is quite a contrast from the past when or native groups were either farmers or — hunters and gatherers who moved between places in search of food. advanced technology has led to the integration of world economics and cultures, in the world's more developed countries. this integration requires , the responsible use and management of natural resources.

Compare demographic and environmental effects of the columbian