The amount of substance left of a radioactive element of half life,

after a time, t, is given by:

Given that <span>potassium-40 has a half life of approximately 1.25 billion
years.
The number of years it will take for 0.1% of potassium-40 to remain is obtained as follows:

Therefore, </span><span>the maximum age of a fossil that we could date using 40k is
12.5 billion years.</span>
Answer:convergent
Step-by-step explanation:
Given
Improper Integral I is given as


integration of
is 
![I=1000\times \left [ e^x\right ]^{0}_{-\infty}](https://tex.z-dn.net/?f=I%3D1000%5Ctimes%20%5Cleft%20%5B%20e%5Ex%5Cright%20%5D%5E%7B0%7D_%7B-%5Cinfty%7D)
![I=1000\times I=\left [ e^0-e^{-\infty}\right ]](https://tex.z-dn.net/?f=I%3D1000%5Ctimes%20I%3D%5Cleft%20%5B%20e%5E0-e%5E%7B-%5Cinfty%7D%5Cright%20%5D)
![I=1000\times \left [ e^0-\frac{1}{e^{\infty}}\right ]](https://tex.z-dn.net/?f=I%3D1000%5Ctimes%20%5Cleft%20%5B%20e%5E0-%5Cfrac%7B1%7D%7Be%5E%7B%5Cinfty%7D%7D%5Cright%20%5D)

so the integration converges to 1000 units
Answer:
C. 17/20, rational
Step-by-step explanation:
.25 + 3/5
The least common denominator is 20 so
.25=1/4=5/20
3/5=12/20; therefore,
5/20 + 12/20=17/20.
17/20 is a fraction so is rational.