Question

How many years will it take for the area of the glacier to decrease to 15 square kilometers

Give an exact answer expressed as a natural logarithm
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Answer 1

20ln(3)

Explanation:

Put 15 for A and solve for t.

15 = 45e^(-.05t)

15/45 = 1/3 = e^(-.05t) . . . . divide by 45

ln(1/3) = -.05t . . . . . . . . . . . take natural logs

20ln(3) = t . . . . . . . . . . . . . . multiply by 20, simplify

It will take 20·ln(3) years for the area to decrease to 15 km^2.