If u-235 has a half-life of 713 million years and the age of the sample is 2.631 billion years old then how many half-lifes has this sample undergone (answer to 2 decimal places)

As the age of the U-235 sample is 2.631 billion years, and the half-life of U-235 is 713 million years, the sample has undergone 2.361 X 1,000,000,000 / 713 X 1,000,000 = 3.69 half lives. In each half-life the sample reduces to half its original weight according to the radioactive Half-Life Formula: ln (Nt /N0) = -kt, where N0 = mass of the original weight of radioactive material, Nt = mass of radioactive material at time t, k = decay constant and t = time interval . We have to put Nt/N0 = 1/2 for time interval = half-life.

=574.9 ft^3

Step-by-step explanation:

The volume of a sphere is V = 4/3 pi r^3

Take half of that to get a hemisphere

1/2 *V = 1/2 *4/3 pi r^3

         =2/3 pi r^3

So the volume of a hemisphere is

V = 2/3 pi r^3

   = 2/3 pi (6.5) ^3

    = 2/3 ( 3.14) * (6.5)^3

    =574.8816667

Rounded to the nearest tenth

   =574.9 ft^3