Question 1208600
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Answer: <font color=red>81.11 mg</font>


Work Shown
P = 215 mg is the starting amount
r = 0.13 is the decimal form of the decay rate
t = 7 days
A = P*(1-r)^t  ............... exponential decay equation
A = 215*(1-0.13)^7
A = 81.109780898733
A = <font color=red>81.11 mg</font>


The 210 is never used since it's part of the name, rather than an amount. 
Some teachers love to place red herrings to distract students.
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