SOLUTION: The formula D=10e^-0.9h can be used to find the number of milligrams D of a certain drug that is in a patients bloodstream h hours after the drug administered. When the number of m

Algebra ->  Logarithm Solvers, Trainers and Word Problems -> SOLUTION: The formula D=10e^-0.9h can be used to find the number of milligrams D of a certain drug that is in a patients bloodstream h hours after the drug administered. When the number of m      Log On


   

Question 1198606: The formula D=10e^-0.9h can be used to find the number of milligrams D of a certain drug that is in a patients bloodstream h hours after the drug administered. When the number of milligrams reaches 2, the drug is to be administered again. What is the time between injections?

Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

D=10e%5E%28-0.9h%29+
When the number of milligrams reaches 2, means D=2
2=10e%5E%28-0.9h%29+
ln%282%29=ln%2810e%5E%28-0.9h%29+%29
ln%282%29=ln%2810%29%2Bln%28e%5E%28-0.9h%29+%29
ln%282%29-ln%282%2A5%29=ln%28e%5E%28-0.9h%29+%29
ln%282%29-%28ln%282%29%2Bln%285%29%29=%28-0.9h%29ln%28e%29
-log%285%29=-0.9h
h=-log%285%29%2F-0.9
h=1.788264347149
h=1.8+hours