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Algebra / Linear equations in one variable Difficulty: Medium

An agricultural scientist studying the growth of corn plants recorded the height of a corn plant at the beginning of a study and the height of the plant each day for the next 12 days. The scientist found that the height of the plant increased by an average of 1.20 centimeters per day for the 12 days. If the height of the plant on the last day of the study was 36.8 centimeters, what was the height, in centimeters, of the corn plant at the beginning of the study?

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Explanation

The correct answer is 22.4. If the height of the plant increased by an average of 1.20 centimeters per day for 12 days, then its total growth over the 12 days was 1 point 2 0, times 12, equals 14.4 centimeters. The plant was 36.8 centimeters tall after 12 days, so at the beginning of the study its height was 36 point 8, minus 14 point 4, equals 22 point 4 centimeters. Note that 22.4 and 112/5 are examples of ways to enter a correct answer.

Alternate approach: The equation 36 point 8 equals, 12, times, 1 point 2 0, plus h can be used to represent this situation, where h is the height of the plant, in centimeters, at the beginning of the study. Solving this equation for h yields 22.4 centimeters.