Answer:
A. 9% per hour
Step-by-step explanation:
we know that
The equation of a exponential decay function is given by
[tex]y=a(1-r)^t[/tex]
where
a is the initial value
r is the rate of decrease
we have
[tex]a=0.23\ kg\\1-r=0.91\\r=1-0.91\\r=0.09[/tex]
Convert to percentage
Multiply by 100
[tex]r=0.09(100)=9\%[/tex]