The mean is defined as the
a. average of a data set.
b. middle of the data set.
c. range of the data set.
d. number that shows up most often in a data set.

A. average of a data set.

Step-by-step explanation:

The mean is defined as the average of a data set.

The word 'average' is a synonym word for ' arithmetic mean' .

It is calculated simply by adding up all the  observations in data then divide by the number of observations.

In other words the mean is it is the sum of all observations divided by the number of observations.

answer: 25.4 units

step-by-step explanation: radius = 12.7 units

diameter = twice the radius

diameter = 12.7 x 2

= 25.4

ab will be equal to