a radio active substance has a half-life of 200 years. We currently have 15 grams of the substance. How much of the substance will still be radioactive 80 years from now?

Question

a radio active substance has a half-life of 200 years. We currently have 15 grams of the substance.  How much of the substance will still be radioactive 80 years from now?

amistre64 · Answer

-ln(2)/200 = rate of decay if i see it correctly

amistre64 · Answer

A = 15 e^(-ln(2)/200 * 80) perhaps?

anonymous · Answer

How long will it take until 1/2 grams of the substance remains radioactive?

amistre64 · Answer

.5 = 15 e^(-kt)

.5/15 = e^(-kt)

ln(.5/15) = -kt

t = ln(.5/15)/(-ln(2)/200) maybe?

amistre64 · Answer

981 years or so .... i think

anonymous · Answer

this should help me thanks

amistre64 · Answer

youre welcome

anonymous · Answer

a one time deposit is made into an account that pays an apr of 8.5% compounded continuously.  How long does  it take for the worth of the account to triple?