Half-life Calculation Question

D??

is it D. 36 hours??

AGREE.
100---50----25-----12.5----6.26

4 HALF TIME = 36 h

totally agree, D

Yes, the right answer is D. 36 hours

can some1 plz explain this,

usmle100 said:

can some1 plz explain this,

Click to expand...

If the 1/2 life =9hrs,it means that it will take 9hrs for 1/2 of the drug to disintegrate making only 50% available,another 9hrs to breakdown 50% of the 50,making it only 25% available,another 9hrs to break 1/2 of that down to 12.5% and then another 9hrs to break it to 6.something %.So,it takes 9hrs x 4 (36hrs) to get 6% of the drug in the system....hope that helps.Pray for me to pass my step 1 and goodluck