To estimate the amount of the federal debt of Country C, we can express it in the form of a single digit times an integer power of 10.
The given federal debt is $278,560,125,000.
First, we can rewrite this amount in scientific notation. To convert this to scientific notation, we want a number between 1 and 10 multiplied by a power of 10:
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Move the decimal point in 278,560,125,000 to the left until one digit remains to the left of the decimal point.
- We move the decimal point 11 places to the left:
- \(2.78560125\)
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Now multiply it by \(10^{11}\) (since we moved the decimal 11 places).
Combining these steps, we have:
\[ 278,560,125,000 \approx 2.79 \times 10^{11} \]
Looking at the provided responses, the closest estimation is:
2.79 × 10²¹
So, the correct answer is: 2.79 × 10¹¹.