Question oil-an

1.1 Linear Functions - Rate of change applications
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Oil and gas production in a certain area dropped from 4 million barrels in 2000 to 1.9 million barrels in 2013. Assuming that the oil and gas production decreased at a constant rate, which of the following linear functions f best models the production, in millions of barrels, t years after the year 2000?

A.

f of t equals, the fraction 21 over 130, end fraction, t plus 4

B.

f of t equals, the fraction 19 over 130, end fraction, t plus 4

C.

f of t equals, the negative fraction 21 over 130, end fraction, t plus 4

D.

f of t equals, the negative fraction 19 over 130, end fraction, t plus 4

Oil and gas production in a certain area dropped from 4 million barrels in 2000 to

Hard-difficulty · SAT Math · Linear Functions — Rate of change applications. Read the question above, select your answer, and check the full explanation below to understand exactly why the correct choice works.

Answer explanation

Choice C is correct. It is assumed that the oil and gas production decreased at a constant rate. Therefore, the function f that best models the production t years after the year 2000 can be written as a linear function, f of t equals, m, t plus b, where m is the rate of change of the oil and gas production and b is the oil and gas production, in millions of barrels, in the year 2000. Since there were 4 million barrels of oil and gas produced in 2000, b equals 4. The rate of change, m, can be calculated as the fraction with numerator 4 minus 1 point 9, and denominator 0 minus 13, end fraction, equals, the negative of the fraction 2 point 1 over 13, which is equivalent to the negative of the fraction 21 over 130, the rate of change in choice C.

Choices A and B are incorrect because each of these functions has a positive rate of change. Since the oil and gas production decreased over time, the rate of change must be negative. Choice D is incorrect. This model may result from misinterpreting 1.9 million barrels as the amount by which the production decreased.