Well, isn't that a happy little question! To find the mean, you add up all the numbers and then divide by how many numbers there are. In this case, with just one number, 31, the mean is simply 31. Keep up the good work, my friend!
14.0
8.8
It is: 276.3 because 0.02 is less than 0.05
9.4
326.6
It is: 21.2
17.2
62.2
The correct answer is 20.0
31,600
13.2 percent (rounded to 1dp).
Circumference of a circle is equal to pi*diameter, or 2*pi*radius, so if d=17.4cm, c=54.7cm (to 1dp), if r=17.4cm, c=109.3cm (to 1dp).