Can someone help me with a word problem?
The number of milligrams of a drug that remains in a patient’s system after t hours is given by the function A(t) = Iert. Don was given 300 milligrams of medicine which leaves his bloodstream at a rate of 20%. How much of the medicine remains in his system after 4 hours?

Question

Can someone help me with a word problem?
The number of milligrams of a drug that remains in a patient’s system after t hours is given by the function A(t) = Iert. Don was given 300 milligrams of medicine which leaves his bloodstream at a rate of 20%. How much of the medicine remains in his system after 4 hours?

lexipoo1998 · Answer

@Luigi0210 @agent0smith 
Can you guys help?

cggurumanjunath · Answer

A(t) = Iert
what is LERT ?

lexipoo1998 · Answer

*IE^rt

lexipoo1998 · Answer

@Euler271 
@ChristopherToni

lexipoo1998 · Answer

Can anyone please help me out?

lexipoo1998 · Answer

The answer choices are 
a. 95.87 mg
b.12.52 mg 
c.134.80 mg
d.31.63 mg

bibby · Answer

Start by identifying the values you have.

l (not sure)
r (rate)
t (time)

lexipoo1998 · Answer

Umm I am not sure but I think it is Ie(capital i not l) u am really lost

bibby · Answer

e is a constant (2.2718..) and I assume l is the dosage

lexipoo1998 · Answer

Oh... wait so how would I solve it? Can you or @Mertsj  walk me through it?

mertsj · Answer

I think you have posted the formula incorrectly.

lexipoo1998 · Answer

It says A(t) = Ie^rt so now I really do not know..

mertsj · Answer

I'm pretty sure the formula is a(t)=Ie^(-rt) but have it your way.

bibby · Answer

Don was given 300 milligrams of medicine which leaves his bloodstream at a rate of 20%. 4 hours.

You clearly have the rate, doseage, e, and the time

lexipoo1998 · Answer

If you can solve it with that then please do @Mertsj  . This is the last question in my workbook packet and i just want to be able to solve it. Can you solve it?

lexipoo1998 · Answer

So do i just mutlply it all out @bibby

mertsj · Answer

I cannot solve it using the formula you posted.

lexipoo1998 · Answer

Can you solve it using something else which will result in one of the answer choices i have been given?

lexipoo1998 · Answer

Well when i multiply it all out i didn't get an answer choice sooo @bibby  what do i do?

mertsj · Answer

Yes.  I can solve it using the correct formula which you refuse to post.

lexipoo1998 · Answer

Alright so this is the formula: a(t)=Ie^(-rt) Can you please solve it now @Mertsj

bibby · Answer

I solved it using mertsj's negative version.

You're not multiplying all the way.
a(t)=Ie^(-rt)

lexipoo1998 · Answer

Did you get 134.80?

bibby · Answer

Yep

lexipoo1998 · Answer

Ok thank you so much!