To find the total number of heartbeats in Massachusetts per year, we can use the following formula:
\[ \text{Total heartbeats} = \text{Average heartbeats per person per year} \times \text{Population} \]
Given:
- Average heartbeats per person per year = \(3.5 \times 10^7\)
- Population of Massachusetts = \(7 \times 10^6\)
Now, we can calculate the total heartbeats:
\[ \text{Total heartbeats} = (3.5 \times 10^7) \times (7 \times 10^6) \]
Using the properties of exponents, we can multiply the coefficients and add the exponents:
\[ \text{Total heartbeats} = (3.5 \times 7) \times (10^7 \times 10^6) = 24.5 \times 10^{13} \]
Now, we need to convert \(24.5\) into scientific notation:
\[ 24.5 = 2.45 \times 10^1 \]
Thus, we adjust our expression:
\[ 24.5 \times 10^{13} = 2.45 \times 10^1 \times 10^{13} = 2.45 \times 10^{14} \]
Therefore, the total number of heartbeats in Massachusetts per year is:
\[ \boxed{2.45 \times 10^{14}} \]