SOLUTION: I would really appreciate some help with this one. The half life of a radio active substance is 125 days. How many days will it take for 82% of the substance to decay?

Question 402769: I would really appreciate some help with this one.
The half life of a radio active substance is 125 days. How many days will it take for 82% of the substance to decay?

Answer by scott8148(6628) (Show Source): You can put this solution on YOUR website!
At = Ao (1/2)^(t/h) ___ At is amount at time t ; Ao is initial amount ; t is the time ; h is the half life

At / Ao = (1/2)^(t/h)

1 - .82 = (1/2)^(t/125)

log(.18) = (t/125)log(1/2)

[log(.18)] / [log(1/2)] = t / 125
RELATED QUESTIONS
a radioactive substance has a half life of 120 days.if an original sample of the... (answered by ankor@dixie-net.com)

The half- life of a radioactive substance is one hundred ninety-four days. How many days... (answered by Edwin McCravy)

The half- life of a radioactive substance is one hundred ninety-four days. How many days... (answered by ankor@dixie-net.com)

A radioactive substance has a half-life of 3.5 days. A scientist starts with 80 grams of... (answered by stanbon)

The amount of grams "A" of a certain radioactive substance dumped in the Craney Island... (answered by stanbon)

The half-life of a radioactive substance is one hundred twenty-five days. How many days... (answered by Theo,Edwin McCravy,ikleyn,greenestamps,MathTherapy)

A substance has a half-life of 52 days. If you have 113 grams initially, how much is left (answered by ikleyn)

A radio active isotope decays according to the exponential decay equation where t is in... (answered by solver91311,Alan3354)

A radio active isotope decays according to the exponential decay equation where t is in... (answered by Cromlix)