Half life of potassium-40,is approximately 1.25 billion years.what will be the fraction of radioactivity left after 5 billion years?

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Answer 1 · 2018-04-20T11:26:26

#1/16 P_0#

#P_0# initial value of potassium

The half-life of potassium is 1.25 billion years. How many times does 1.25 go in 5 billion years?

#5/1.25=4#

There are #4# half-lives.

#1)# #1/2 P_0#

#2)# #1/2(1/2P_0)#

#3)# #1/2(1/2*1/2P_0)#

#4)# #1/2(1/2*1/2*1/2P_0)#

So after five billion years, it will be #1/16 P_0#.