Question

The number of kilograms, y, of a radioactive element that remains after t hours can be modeled by the equation y = 0.23 ( 0.91 ) t . What is the rate of decrease of this radioactive element? A. 9% per hour B. 23% per hour C. 77% per hour D. 91% per hour

Answer 1

A. 9% per hour

Explanation:

we know that

The equation of a exponential decay function is given by

`y=a(1-r)^t`

where

a is the initial value

r is the rate of decrease

we have

`a=0.23\ kg\\1-r=0.91\\r=1-0.91\\r=0.09`

Convert to percentage

Multiply by 100

`r=0.09(100)=9\%`