Arubidium isotope has a half-life of almost 50 billion years. given that scientists estimate earth's age to be 4.6 billion years, what is the most likely percentage of parent to daughter isotopes of this element currently existing on earth?

less than 10 percent
25 percent
50 percent
more than 75 percent

If we review the changes in the landscape surrounding the great salt lake in utah we can see a change in topography. look at the area to the south of the lake. what change has occurred during the last twenty-nine years? a) erosion of the hills b) an increase in marshland c) flooding of the area and the development of wetlands d) deposition of sediments and an increase in elevation