Exponential and Logarithmic functions
posted by Sara .
A certain material decays at a rate of 1.9% per year. The sample is 260 grams. How much will be left in 11 years? How long will it take to have only a 100g sample left?

Exponential and Logarithmic functions 
Reiny
decay rate = 1.9% = .019
amount of the 260 g left after 11 years
= 260(.981)^11
= ...
b) when are left with 100 g ?
260(.981)^n = 100
.981^n = .384615...
take log of both sides and use log rules:
n log .981 = log .384615...
continue 
Exponential and Logarithmic functions 
Sara
Thank you
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