Question

A radioactive substance decays at a rate of 6% each year. If the initial amount of the substance was 600 grams, create an exponential function to model the decay of the substance. Which of the following options correctly models the decay?
The option that correctly models the problem is Option #C
Option #1: f(x) = 600(0.06)*

Option #2: f (x) = 600(1.06)*

Option #3: f(x) = 600(0.6)=

Option #4: f(x) = 600(0.94)*

Answer 1

Use the decay factor 1 − 0.06 = 0.94. With t in years the amount is

f(t) = 600(0.94)^t, t ≥ 0.

So the correct choice is Option #4. (Option 2 is growth, Option 1 and 3 use the wrong factors/format.)