# Thread: Half - Life Question!

1. ## Half - Life Question!

Hello,

At the beginning of an experiment, a scientist has 120 grams of radioactive goo. After 135 minutes, her sample has decayed to 15 grams.

half life would be 45 per my calculation..

but this is the part that is troubling me:

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

2. can anyone think of an equation?

i can only think of g(t) = 120/(2^t/45)

but this is not the right answer supposedly

3. Originally Posted by frozenflames
Hello,

At the beginning of an experiment, a scientist has 120 grams of radioactive goo. After 135 minutes, her sample has decayed to 15 grams.

half life would be 45 per my calculation..

but this is the part that is troubling me:

Find a formula for G(t), the amount of goo remaining at time t. G(t) =
Read this: Half-life - Wikipedia, the free encyclopedia

$\displaystyle G(t) = 120 \left( \frac{1}{2} \right)^{t/45} = \frac{120}{2^{t/45}}$ (so the reply given in reply #2 is OK).