Question

The mean of the data set is 15. What number is missing of these data set: 18, 16, - 9, 12, 23

Answer 1

$x = (15 \times total \: set \: size) - (given \: set \: sum) \\ x = (15 \times 6) - (60) \\ x = 90 - 60 \\ x = 30$

Answer 2

A mean is an arithmetic average of a set of observations. The number that is missing in the data set whose sum is 90 is 30.

What is Mean?

A mean is an arithmetic average of a set of observations. it is given by the formula,

${\rm Mean=\dfrac{\sum Data\ points}{Number\ of\ Data\ points}}$

Let the number that is missing in the data set be x.

Since the mean of the data set is 15, while the set contains numbers 18, 16, - 9, 12, 23 and x. Therefore, the mean can be written as,

${\rm Mean=\dfrac{\sum Data\ points}{Number\ of\ Data\ points}}\\\\\\15=\dfrac{18+16-9+12+23+x}{6}\\\\\\90 = 18+16-9+12+23+x\\\\90=60+x\\\\x = 30$

Thus, the number that is missing in the data set whose sum is 90 is 30.

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