In the scenario where the number of people who have heard a rumor doubles each day, starting with 3 people, you can model this situation using an exponential growth equation.
Let \( P(t) \) represent the number of people who have heard the rumor after \( t \) days. Given that the number of people doubles each day, we can write the equation as:
\[ P(t) = P_0 \cdot 2^t \]
where \( P_0 \) is the initial number of people who have heard the rumor. Since we start with 3 people, we have:
\[ P_0 = 3 \]
Therefore, the equation that represents the scenario will be:
\[ P(t) = 3 \cdot 2^t \]
Here, \( t \) is the number of days since the rumor started spreading.