The quantity Q remaining of a substance whose initial value is Q_0 is given by Q=Q_0 e^-0.0003t where is the time in years. Find the time needed for 75% of this substance to disintegrate to the nearest year.
thankyou
Math interest rates question
2010-03-15 1:19 pm
回答 (3)
2010-03-15 4:10 pm
✔ 最佳答案
Let Q_0 be Aso Q = Ae^(-0.0003t)
since 75% of A is disintegrated, remaining will be 25% of A.
so 0.25A = Ae^(-0.0003t)
log 0.25 = - 0.0003t
t = log 0.25/(-0.0003) = 2007 years.
2010-03-15 08:13:10 補充：
Correction: Sorry, I should use natural log instead of common log, so answer should be
ln 0.25/(-0.0003) = 4621 years.
2010-03-17 3:09 pm
the answer is right,i just check it
thx a lot
thx a lot
2010-03-16 4:47 pm
this is not an interest question. It is a time-decay question
收錄日期: 2021-04-23 18:24:20
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