Question

A collection of 5 positive integers has mean 4.4, unique mode 3 and median 4. If an 8 is added to the collection, what is the new median. Express your answer as a decimal rounded to the nearest tenth.

Answer 1

9514 1404 393

Answer:

  4.5

Step-by-step explanation:

It appears the 5 integers must be {3, 3, 4, 5, 7}.

For the mode to be unique, there must be more than one '3', and there cannot be any other repeated numbers. For 4 to be the median, it must be the 3rd-highest number. Then the remaining numbers must be integers greater than 4 with a sum of 12 for the mean to be 4.4.

When 8 is added to the collection, the median is now the average of 4 and 5, so is 4.5.

The new median is 4.5.

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Comment on vocabulary

mean: the sum of numbers divided by the number of numbers. 5 numbers with a mean of 4.4 will have a sum of 5×4.4 = 22.

median: the middle number of a collection of an odd number of numbers, when sorted from lowest to highest. It is the 3rd number of a group of 5 numbers. When there are an even number of numbers in the group, the median is the average of the middle two in the sorted list. Here, that means the 3rd number in the list of 5 is '4'. When 8 is added, 4 becomes one of the numbers contributing to the average that will be the new median.

mode: the member of the group that appears the most times. When the mode is unique, it means there are no other numbers repeated as often. Here, we know the 3rd number (of 5) is 4, so there can only be two numbers '3' in the collection. That 3 is the unique mode means no other numbers are repeated at all.