I need help with a word problem?

Question

The function D(h)=5e^-0.4(h) can be used to determine the milligrams D of a certain drug in a patient's bloodstream h hours after the drug has been given. How many milligrams (to two decimals) will be present after 7 hours. I don't know what to do with the "e" I need a decimal but I arrive at 5/e^28 and don't know what to do next.

Answer 1

I dont have an answer for u..

Answer 2

If e is not a variable, it looks like it's a Euler which is 2.71828183, so just evaluate with that in place of e and use the right number of significant figures.

Answer 3

"e" is a constant. It shows up on almost every calculator made.

Its value is 2.7182818281828......

Use the windows calculator or use Google. I typed in exactly what you wrote and got an answer. So give it a go. I'm getting 0.30 mg present after 7 hrs.

Hope this helps.

:)

p.s. Note....IF you decide to try the illustrious Windows calculator you will think that "e" is not included....but...it IS included. Windows expects you to know that the natural logarithm "ln(x) is the inverse of "e". So if you want to use 'e', you have to put in the number you want to raise 'e' to and then check the inverse box and then click the ln button.

Answer 4

after 7 hours the amount of drug left is

D(7) = 5 e ^ (-2.8) = 5 * 0.0608 = 0.304

The link below would explain how to read exponential tables