A radioactive substance decays exponentially. A scientist begins with 130 milligrams of a radioactive substance. After 24 hours, 65 mg of the substance remains. How many milligrams will remain after 45 hours?

Question

anonymous · Answer

$$N(t) = N * .5^{t/h} $$ where n(t) is amount of substance left, N = initial amount, t = current time, and h = half-life time.
h = 24 hours t= 45 hours, N = 130mg

therefore, $$N(t) = 130 * .5 ^{45/24} = 35.44mg$$

anonymous · Answer

you are given the half life is 24 hours.  so the formula is 
$$A = 130(\frac{1}{2})^{\frac{t}{24}}$$
replace t by 45
daniel has it!

anonymous · Answer

thank you!:)