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Change in the mean when a number is removed

Find the change in the mean when a number is removed

This math skill describes how to determine which number in a set must be removed to achieve a specific decrease in the mean of the remaining numbers. It involves calculating the original mean, determining the new desired mean, and finding which number's removal results in the sum that matches the new mean times the remaining number of elements.

Learn change in the mean when a number is removed

Teaching Transcript

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What number can be removed for the mean to decrease by 2?

Adding the numbers and dividing by 3 gives an original mean of 5

Since it goes down by 2, that means it becomes a mean of 3

And we will only have 2 numbers, so they must sum to 6

Zero and six will add to six, so let's remove the 9

Skill Practice

Find the change in the mean when a number is removed

Test your understanding of change in the mean when a number is removed by practicing it! Work through the below exercises to use it in practice.