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March 4, 2015

March 4, 2015

Posted by **Hayli** on Tuesday, September 14, 2010 at 7:17pm.

(a) Determine when 2 milligrams is left in the body.

(b) What is the half-life of the drug?

- Pre Calc! -
**MathMate**, Tuesday, September 14, 2010 at 7:28pma)

A(t)=A0(0.8)^t

For 2 mg left, we have A(t)=2, A0=10, so

2=10(0.8)^t

0.8^t = 1/5

take ln on both sides,

t*ln(0.8)=ln(1/5)

t=ln(0.2)/ln(0.8)

=7.2 hours

b)

Half-life is the time it takes to reduce the quantity to 0.5A0, i.e.

5=10(0.8)^t

solve for t similar to a) above.

- Pre Calc! -
**Hayli**, Tuesday, September 14, 2010 at 7:46pmThank you!

- Pre Calc! -
**MathMate**, Tuesday, September 14, 2010 at 8:08pmYou're welcome!

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