Question

Iodine-131 is a radioactive material with half-life of eight days. A scientist starts with 100 grams of iodinie- 131. Which function can be used to estimate the number of grams of iodine-131 remaining at the end of x days?

A. f(x)= 100(0.92)^x

B. f(x)= 100 (1.09)^x

C. f(x)= (0.92)^x

D. f(x)= (1.090^x

Answer 1

The correct answer is Choice A.

This is an example of an exponential equation, so we need the formula
`y=ab^x`.

The a value is the starting value of 100. The b value must be a decimal lower than 1 because it is decreases.

If you substitute in 8 for x, you will see that the output is about 50 (half of 100).