Question

Mike forgot to replace the cap on a bottle of room freshener. The room freshener began to evaporate at the rate of 15% per day. If the original amount of room freshener in the bottle was 40 grams, which of the following graphs best represents the amount of room freshener f(x) that would remain in the bottle after x days?

graph of function f of x equals 30 multiplied by 0.88 to the power of x
graph of exponential function going down from left to right in quadrant 1 through the point 0, 40 and approaching the x axis
graph of function f of x equals 50 multiplied by 0.82 to the power of x
graph of exponential function going down from left to right in quadrant 1 through the point 0, 4 and approaching the x axis

Answer 1

its stated that:
\[ \text{rate of evaporating} \rightarrow 15 \% /d \]
we're asked to find the REMAINING ammount, not the evaporated ammount:
\[100\%-15\%=85\% \rightarrow \color{lightskyblue}{0.85}\]
\[ \text{ initial freshener ammount } \rightarrow \color{tomato}{40} \ g \]

having that info we can write that the amount of freshener that would REMAIN in the bottle will be:
\[ f(x) = \color{tomato}{40} \times \color{lightskyblue}{0.85}^{x_{days}} \]
the graph looks like this (image attached )

knowing all that, it's literally in front of you -- can you pull the answer?