Posted by **Jus** on Thursday, May 21, 2009 at 2:58pm.

When you drink a cup of coffee or a glass of cola, or when you eat a chocolate bar, the percent, P, of caffeine remaining in your bloodstream is related to the elapsed time, t, in hours, by t=5(logP/log0.5).

a) how long will it take for the amount of caffeine to drop to 20% of the amount consumed?

My answer (which is correct)

= 11.6

b) suppose you drink a cup of coffee at 9 am. What percent of the caffeine will remain in your body at noon?

My attempt:

9=5(logP/log0.5)

then I solved for P, but the answer is wrong.

Could you please help me with part b?