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Question

The following observations are arranged in ascending order. If the median of the data is 19, then find the value of x.
6, 9, 15, x + 4, x + 8, x + 12, 30, 32

This question was previously asked in
RRB NTPC 2019 CBT 1 Question Paper (8-Mar-2021) (Shift 2)
The correct answer is
13

The problem asks us to find the value of x given a dataset arranged in ascending order and its median.

Understanding Median Calculation

The dataset provided is: 6, 9, 15, x + 4, x + 8, x + 12, 30, 32. There are 8 observations in total (n=8). Since 'n' is an even number, the median is calculated as the average of the two middle observations.

  • The middle positions are the $\frac{n}{2}$th and $(\frac{n}{2} + 1)$th observations.
  • For n=8, these are the $\frac{8}{2} = 4$th and $(\frac{8}{2} + 1) = 5$th observations.

Calculating the Value of x

The 4th observation is x + 4 and the 5th observation is x + 8. The median is given as 19.

Using the median formula:

$ \text{Median} = \frac{(\text{4th observation}) + (\text{5th observation})}{2} $

Substitute the values:

$ 19 = \frac{(x + 4) + (x + 8)}{2} $

Now, solve for x:

  1. Simplify the numerator: $19 = \frac{2x + 12}{2}$
  2. Multiply both sides by 2: $19 \times 2 = 2x + 12$
  3. $38 = 2x + 12$
  4. Subtract 12 from both sides: $38 - 12 = 2x$
  5. $26 = 2x$
  6. Divide by 2: $x = \frac{26}{2}$
  7. $x = 13$

Therefore, the value of x is 13.

Verification

If x=13, the data becomes: 6, 9, 15, (13+4), (13+8), (13+12), 30, 32, which is 6, 9, 15, 17, 21, 25, 30, 32. The median is $\frac{17 + 21}{2} = \frac{38}{2} = 19$. This confirms our result.

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Similar Questions

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    17, 19, 12, 20, 19, 14, 15, 18, 19, 14
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Important Questions from Elementary Statistics

  1. In a colony 5 families have 1 child, 7 families have 2 children, 8 families have 3 children and 3 families have 4 children.What is the mode of the number of children.

  2. What will be the difference between mean and median of the given data?

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