Answer: 115
Explanation: Given ,
Half life of Strontium-90 = 28.8 years.
Number of count sample(s) = 5
Decay Sample counts (d)= 0.3125
Time taken for a 5-count sample to decay 0.3125 =?
1 - First calculate (d/s) i.e (0.3125/5) = 0.0625.
2- since its half life (1/2)^n i.e (1/2)^n = 0.0625
n log 0.5 = log0.0625
n = (log0.0625/0.5) = 4.
(1/2)^4 =(1/16)=0.0625 =>28.8 times 4 i.e 115.2 years.
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