Answer:
4.5
Step-by-step explanation:
To find the eighth number, we need to consider how the median is affected by adding another number.
Since the median of the 8 numbers is given as 4.5, this means that when the numbers are arranged in ascending order, the fourth and fifth numbers (out of the eight) will be 4 and 5, respectively.
Given that seven of the numbers are 9, 2, 3, 4, 12, 13, and 1, the eighth number must be inserted between the 4 and 5.
If we assume the eighth number to be \( x \), then the ordered sequence would be:
\[ 1, 2, 3, 4, x, 9, 12, 13 \]
Since the median is 4.5, the number in the middle of the ordered sequence (when arranged in ascending order) should be 4.5.
So, in this case, \( x = 4.5 \).
Therefore, the eighth number is 4.5.
