If at the formation of the Earth we had a rock with 1000 atoms of Potassium-40 inside, about how many Argon-40 atoms would be found in that rock today?

Question

Potassium-40 decays to Argon-40 with a half-life of 1.25 billion years.

 

Multiple choice options

 

<<1

1 

25

100

250

500

999

Answer 1

A = a₀(0.5)^t/h

A = 1000(0.5)^(4.54/1.25)

A = 1000(0.5)^3.632

A = 1000(0.080660155)

 

What is A?