To determine the remaining level of a substance after a certain period of time, you can use the formula for exponential decay based on the concept of half-life. The amount remaining after time \( t \) can be modeled by the equation:
\[ y = y_0 \left( \frac{1}{2} \right)^{\frac{t}{\text{half-life}}} \]
Where:
- \( y_0 \) is the initial amount (674 mg/L in this case),
- \( t \) is the total time elapsed,
- and the half-life is the time it takes for the substance to reduce to half its initial value (9 hours).
For a time of 1 day, we first need to convert days to hours. Since 1 day = 24 hours, we will use \( t = 24 \) hours.
Now, we plug these values into our formula:
\[ y = 674 \left( \frac{1}{2} \right)^{\frac{24}{9}} \]
Thus, the equation that best helps to determine the remaining level after 1 day is:
\[ y = 674 \left( \frac{1}{2} \right)^{\frac{24}{9}} \]
So the correct choice from the options provided is:
y = 674(1/2)^(24/9)
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