Question 706104
    Ok this involves using growth and decay equations it says "a material decays at a rate of 1.1% per year .if you start with 250 grams of the material, in how many years will there be 100 grams remaining?" And it wants me to find the right equation to start off with can you help me?
.
The exponential growth/decay equation is:
A = Pe^(rt)
where
A is amount after time t (100)
P is initial amount (250 grams)
r is rate (-.011) (r<0 for decay)
t is time (what we're looking for)
.
100 = 250e^(-.011t)
100/250 = e^(-.011t)
2/5 = e^(-.011t)
ln(2/5) = -.011t
ln(2/5)/(-.011) = t
83.3 years = t