The function $N(t)$ gives a number "in thousands". What does it mean if $N(t)$ equals some number like $86.4$?

Once you know what $t=3$ means and what $N(t)$ measures, describe in a full sentence what it means that $N(3)$ is approximately $86.4$.

Type 50*(1.2)^3 into Desmos and look at the numeric result. This is the value of $N(3)$ according to the model; use it to understand how many thousands of downloads the model predicts at $t=3$ days.

The function is $N(t) = 50(1.2)^t$.

• The input $t$ is the number of days after the app is released.
• The output $N(t)$ is the predicted number of downloads, in thousands.

So any statement about $N(t)$ must talk about a certain number of days after release and a number of downloads in thousands.

$N(3)$ means we plug in $t=3$ into the function. Since $t$ is the number of days after release, $t=3$ represents 3 days after the app is released.

So $N(3)$ is the predicted number of downloads (in thousands) 3 days after release.

If $N(3) \approx 86.4$ and $N(t)$ is measured in thousands of downloads, then $N(3)$ represents approximately $86.4$ thousand downloads.

Putting it in a full sentence: 3 days after release, the predicted number of downloads was approximately 86.4 thousand. This matches answer choice C.