math30
posted by alejandro on .
The mass of a radioactive sample is represented in the graph below. The initial mass of 32 mg decays to 8 mg after 21 hours.
1)What is the halflife of the radioactive sample, in minutes?
2)Solve each equation.
a. 4 8x1 = 8
b. 3^(2x5) = 1/27x

8 is 1/4 of 32, so two halflives = 21 hours.
halflife is 10.5 hours
4^(8x1) = (2^2)^(8x1) = 2^(16x2) = 8 = 2^3
so, 16x2 = 3
x = 5/16
assuming 1/27x = (1/27)*x,
3^(2x5) = (3^3)x
(2x5)log3 = 3log3 + logx
(2x2)log3 = logx
nope
assuming a typo, and the x on the right does not belong,
3^(2x5) = 1/27 = 3^3, so
2x5 = 3
x = 1