In an unweathered sample of detrital sedimentary rock, the ratio of an unstable isotope to its stable daughter isotope is 1/15. If no daughters were present at the time the rock cooled below closure temperature, and the half-life of the reaction is 50 million years, how old is the rock?

a. 200 million years
b. 400 million years
c. 750 million years
d. None of the above are correct

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.

What was the first official pair of sister cities?

Which evidence is most likely used to indicate the beginning of solar system formation? a. materials combined to form a mass. b. materials were pulled together by gravity. c. water condensed and collected to form oceans. d. different species of microorganisms lived on earth.