To express the federal debt of Country C, $278,560,125,000, in the form of a single digit times an integer power of 10, we can rewrite the number in scientific notation.
The number $278,560,125,000 can be approximated as follows:
- Identify the first significant digit: 2.
- Move the decimal point to the right until only one digit is to the left of the decimal: 2.78560125.
- Count how many places you moved the decimal: from the end of the number (11 places to the left).
- Thus, the expression in scientific notation becomes \( 2.78560125 \times 10^{11} \).
Since we need to express it in a single digit times an integer power of 10 and find the closest estimation, we round \( 2.78560125 \) to \( 2.79 \).
Hence, the closest approximation is: \[ 2.79 \times 10^{11} \]
Therefore, the final answer is: \[ \text{2.79 × 10}^{11} \]