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Problem-Solving and Data Analysis Difficulty: Medium

If a is the mean and b is the median of nine consecutive integers, what is the value of the absolute value of, a, minus b, end absolute value ?

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Explanation

The correct answer is 0. Any nine consecutive integers can be written as k, k plus 1, k plus 2, k plus 3, k plus 4, k plus 5, k plus 6, k plus 7, k plus 8. The mean of the integers is their sum divided by 9: the fraction with numerator open parenthesis, k plus, k plus 1, plus, k plus 2, plus, dot dot dot, plus, k plus 8, close parenthesis, and denominator 9, equals, the fraction with numerator, open parenthesis, 9 k plus 36, close parenthesis, and denominator 9, which simplifies to k plus 4. So a, equals, k plus 4. Since there is an odd number of integers (nine), the median is the integer in the middle when all the integers are ordered from least to greatest: k plus 4. So b equals, k plus 4. Therefore, the absolute value of a, minus b, end absolute value, equals, the absolute value of, open parenthesis, k plus 4, close parenthesis, minus, open parenthesis, k plus 4, close parenthesis, end absolute value, which is 0.