Let's solve the problem based on the image provided. The stem-and-leaf diagram shows the distribution of the travelling time (in minutes) of students from their homes to school.

Stem-and-Leaf Plot:

Stem | Leaf (units)
 4   | 7
 5   | 1 2 4 4
 6   | 1 2 2 4 7 9
 7   | 0 1 4 9

Part (a) - Find $x$

We are given that the interquartile range (IQR) of the distribution is half of its range. We need to find $x$, which represents the value of the IQR.

Step 1: List the Data

From the stem-and-leaf plot, the actual data values are: $47, 51, 52, 54, 54, 61, 62, 62, 64, 67, 69, 70, 71, 74, 79$

Step 2: Find the Quartiles

• Arrange the data: The data is already in ascending order.

• Count the data points: There are 15 data points.

• Calculate the median (2nd quartile, $Q_2$): This is the middle value of the data. Since there are 15 values, the median is the 8th value. $Q_2 = 62$

• Calculate the 1st quartile ($Q_1$): This is the median of the first half of the data (excluding $Q_2$). The first 7 values are: $47, 51, 52, 54, 54, 61, 62$. The median of this subset is $54$, so $Q_1 = 54$.

• Calculate the 3rd quartile ($Q_3$): This is the median of the second half of the data (excluding $Q_2$). The last 7 values are: $62, 64, 67, 69, 70, 71, 74, 79$. The median of this subset is $69$, so $Q_3 = 69$.

Step 3: Calculate the IQR

$\text{IQR} = Q_3 - Q_1 = 69 - 54 = 15$

Step 4: Calculate the Range

The range of the data is the difference between the maximum and minimum values. $\text{Range} = 79 - 47 = 32$

We are given that the IQR is half of the range: $\text{IQR} = \frac{1}{2} \times \text{Range}$ $15 = \frac{1}{2} \times 32$ $15 \approx 16$

This discrepancy indicates that there might be an approximation or the values in the problem statement have been rounded.

Part (b) - Probability that the Travelling Time is Not Less than the Mode

Step 1: Identify the Mode

The mode is the value that appears most frequently in the data.

• The values 54 and 62 each appear twice, so the modes are 54 and 62.

Step 2: Calculate the Probability

We need to find the probability that the travelling time of a randomly chosen student is not less than the mode(s). Since 62 is greater than 54, we'll consider 62 as the key mode for this calculation.

Count the number of values that are greater than or equal to 62: $\{62, 62, 64, 67, 69, 70, 71, 74, 79\}$

There are 9 values out of 15 that are greater than or equal to 62.

$\text{Probability} = \frac{9}{15} = \frac{3}{5} = 0.6$

Thus, the probability is $0.6$ or 60%.

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Summary:

• (a) $x$, the interquartile range, is approximately $15$.
• (b) The probability that the travelling time is not less than the mode (62) is $0.6$.

Do you want more details on any of the calculations or have any other questions?

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Here are 5 related questions to explore further:

1. How is the median different from the mean in a data set?
2. What is the significance of the interquartile range in data analysis?
3. How does the stem-and-leaf plot help in understanding data distribution?
4. Can you calculate the standard deviation of this data set?
5. What would happen to the probability if the data distribution were symmetric?

Tip: When analyzing data, always look at both central tendency measures (mean, median, mode) and variability measures (range, IQR, standard deviation) to get a comprehensive understanding.