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:
=760
Step-by-step explanation:
Area: 
diameter= 44
radios= 22
area of full circle:
3.14(22)^2
= 1519.76
Area of half circle"
1519.76/2= 759.88
=760
Answer:
28.3 (explaination below)! :)
Step-by-step explanation:
Use the formula for cicrumfrence: C=2πr
Radius can be found by splitting the given number in half, (unless you were given the radius already, then you'd just multiply by 2).
Plug in our numbers. C= 2π4.5
Then, multiply.
You'd get 28.27433388230814.
Rounding to the first decimal place, you'd have a final answer of 28.3.
Hope this helps!
Answer:
He mows 80 yards.
Make meh happy pls ;)
Step-by-step explanation: