The sum of the populations of the two cities is calculated by adding the two populations together.
3.45 × 10^6 + 1.3 × 10^5
To add these numbers, we need to have the same exponent for the powers of 10. We can do this by manipulating 1.3 × 10^5.
We can write 1.3 × 10^5 as 0.13 × 10^6, since dividing by 10 is equivalent to moving the decimal point one place to the left.
So, the sum of the populations is:
3.45 × 10^6 + 0.13 × 10^6 = 3.58 × 10^6
Thus, the sum of the populations of the two cities in scientific notation is 3.58 × 10^6.