# Half life

• October 2nd 2011, 10:07 AM
habibixox
Half life
At the beginning of an experiment, a scientist has 100 grams of radioactive goo. After 225 minutes, her sample has decayed to 12.5 grams.

1. What is the half-life of the goo in minutes?

2. Find a formula for G(t), the amount of goo remaining at time t. G(t) =

3. How many grams of goo will remain after 41 minutes?

I got 1. It is 75 minutes

how do you find a formula???
• October 2nd 2011, 11:48 AM
skeeter
Re: Half life
$G(t) = G_0 \left(\frac{1}{2}\right)^\frac{t}{h}$

$G_0$ = amount at time $t = 0$

$h$ = half-life
• October 2nd 2011, 12:07 PM
habibixox
Re: Half life
so that is the formula for number 2?
• October 2nd 2011, 12:10 PM
habibixox
Re: Half life
100(1/2)^(t/75)

that's the forumla.
now i just plug in 41 minutes for t.