To express 100,000 as a power of 10, we can recognize that 100,000 equals 10 to the power of 5 since \(10 \times 10 \times 10 \times 10 \times 10 = 100,000\).
Thus, the answer to the first question is:
\[
A5
\]
For the second question, we are given that one light-year is approximately \(10^{16}\) meters. We are asked to find out how many meters across the entire Milky Way galaxy is.
The Milky Way is approximately 100,000 light-years across. To convert this to meters, we multiply the number of light-years by the number of meters in one light-year:
\[
100,000 \text{ light-years} \times 10^{16} \text{ meters/light-year} = 100,000 \times 10^{16} \text{ meters}
\]
Now, to put this into a base 10 format, we first represent 100,000 in terms of a power of 10, which we've already determined to be \(10^5\). So, the calculation becomes:
\[
10^5 \times 10^{16} = 10^{5+16} = 10^{21} \text{ meters}
\]
Therefore, the Milky Way galaxy is about \(10^{21}\) meters across.
The answer to the second question is:
\[
10^{21}
\]
