Ten observations 5, 9, 14, 15, x+1, 2x-13, 28, 30, 32, 34 are written in…

2017

Ten observations 5, 9, 14, 15, x+1, 2x-13, 28, 30, 32, 34 are written in ascending order. The median of the data is 24. Find the value of x.

  1. A.

    20

  2. B.

    19

  3. C.

    21

  4. D.

    16

Attempted by 5 students.

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Correct answer: A

For any set of n observations arranged in ascending order, the median is defined differently depending on whether n is odd or even. When n is even, there is no single middle observation, so the median is defined as the average of the two central terms — the (n/2)-th and the (n/2 + 1)-th observations in the sorted list.

  1. Here n = 10, an even count, so the median is the average of the 5th and 6th terms in the ascending list.

  2. From the given ascending sequence 5, 9, 14, 15, x+1, 2x-13, 28, 30, 32, 34, the 5th term is x+1 and the 6th term is 2x-13.

  3. Since the median is given as 24, set up the equation: (x + 1 + 2x - 13) / 2 = 24.

  4. Simplify the numerator: (3x - 12) / 2 = 24.

  5. Multiply both sides by 2: 3x - 12 = 48.

  6. Add 12 to both sides: 3x = 60.

  7. Divide by 3: x = 20.

Substituting x = 20 back into the sequence gives the 5th term = 21 and the 6th term = 27. The full ordered sequence 5, 9, 14, 15, 21, 27, 28, 30, 32, 34 remains correctly in ascending order, and the average of the two middle terms is (21 + 27) / 2 = 24, which matches the given median — confirming the value is correct.

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