Question about geometric series

**yida** · June 1st 2010, 12:38 PM

I don't quite understand half-life. How to solve this question?

**skeeter** · June 1st 2010, 01:54 PM

Originally Posted by yida

I don't quite understand half-life. How to solve this question?

$y = y_0\left(\frac{1}{2}\right)^{\frac{t}{h}}$

$y$ = amount left at any time $t$ in hrs

$y_0$ = amount at $t = 0$

$h$ = half-life in hrs

**yida** · June 1st 2010, 02:27 PM

the answer is wrong

**skeeter** · June 1st 2010, 03:54 PM

Originally Posted by yida

the answer is wrong

what answer are you speaking of ?

I gave you the general function for half-life, not an "answer".

**yida** · June 1st 2010, 03:58 PM

I use y0=55
t=12 h=7.2
but I got wrong answer

**skeeter** · June 1st 2010, 04:01 PM

what "wrong answer" did you get?

**yida** · June 1st 2010, 04:04 PM

55(0.5)^(12/7.2)

**skeeter** · June 1st 2010, 04:07 PM

Originally Posted by yida

55(0.5)^(12/7.2) = 17.324 mg

... and that is not wrong.

Thread: Question about geometric series