Answer:
i belive its 1
Step-by-step explanation:
Because its SUM so its adding and the sum is 22 and 20+2=22.
It is the lateral edge as it is an edge and it is on the lateral area.
you divide 72 by 2 to get r by itself and get 36
so r=36
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>