100grams of a certain element has decayed to 50 grams in 5 years.Find to the nearest integer the rate of decay
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100grams of a certain element has decayed to 50 grams in 5 years.Find to the nearest integer the rate of decay

[From: ] [author: ] [Date: 11-08-15] [Hit: ]
!!-fraction remaining = e^kt ,0.5k = ln 0.k = ln 0.......
100 grams of a certain element has decayed to 50 grams in 5 years. Find, to the nearest integer, the rate of decay.

Please show me how to solve this
Best answer gets ten points!!!!

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fraction remaining = e^kt , so
0.5 = e^5k
5k = ln 0.5
k = ln 0.5/5 = -0.1386 <------------
equivalent to a continuous decay rate of 13.86% => 14% <----------

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... An = Ao (1/2)^(n/half-life)
or 50 = 100 (1/2)^(5/half-life)
or (1/2)^(1) = (1/2)^(5/half-life)
or 1 = 5/half-life
or half-life = 5 years
or decay-rate = 5 / ln(2) = 7.213475204444817
1
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