Question

No idea how to solve this..
The half-life of radium is 1690 years. If 10 grams is present now, how much will be present in 50 years?

Answer 1

here first of all find the disintegrating constant

Answer 2

i am not sure abt the formula but
it is somewhat like
disintegrating constant =0.693/(hal-life time)

Answer 3

then use
ln (amt present after t yrs/amt initially present) = -(disintegrating constant)* time

Answer 4

@Kira_Yamato Can you explain how you did it?

Answer 5

radio active decay problems modelled by : \(\large y=Ce^{kt} \)
where C is your initial amount (10 grams), and k is your "disintegrating" constant as explained by @matricked.

you'll need to find k so you'll need to solve the equation: \(\large 5=10e^{k \cdot 1690} \)
because the half-life is 1690 years, there will only be 5 grams left of the original 10 grams when 1690 years have elapsed. This is what @Kira Yamato did above. k=-(ln2)/1690.

So the model for the half-life decay is: \(\large y=10e^{(-\frac{ln2}{1690}\cdot t)} \)
To answer your question, use a calculator to find y when t=50 years.

Answer 6

@dpaInc
@toadytica305
@Kira_Yamato
that's how you solve the problem.
we do not need to stick a negative sign to K because when you solve K will be negative.