Answer:
The current amount of the Potassium-40 sample is approximately 37.521 grams.
Explanation:
The amount of the sample of the radioactive isotope decays exponentially in time, the amount of mass of the sample as a function of time (
), in grams, is described below:
(1)
Where:
- Initial mass, in grams.
- Time, in years.
- Time constant, in years.
The time constant can be found from half life (
), in years, described in statement:
(2)
If we know that 
, 
and 
, then the current amount of the sample is:
The current amount of the Potassium-40 sample is approximately 37.521 grams.
Because the Moon<span> rotates </span>on<span> its axis at the same rate that the </span>Moon<span> orbits the </span>Earth<span>, </span>a<span> situation known as synchronous rotation or tidal locking. The </span>Moon is <span>directly illuminated by the Sun, and the cyclically varying viewing conditions cause the lunar phases.
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