**a.**

Find an exponential function to model the percent of impurity left after the kerosene travels *x* feet.

of the impurities are removed for every foot.

Since of the impurities are removed for every foot remaining impurities .

The percent of impurity left after the kerosene travels *x* feet is .** **

**b.**

The function .

Graph of the function .

**c.**

Find percent of the impurity remains after the kerosene travels feet.

Substitute in .

.

Percent of the impurity remains after the kerosene travels feet is .

**d. **

No, because the graph has a horizontal asymptote , so the percentage of impurities never reach to .

**a.**

The percent of impurity left after the kerosene travels *x* feet is .

**b.**

Graph of the function is :

**c.**

Percent of the impurity remains after the kerosene travels feet is .

**d. **

The percentage of impurities never reach to .

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