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!
8.8
8.91 to one decimal place (1dp) is 8.9. This is achieved by rounding the number to the nearest tenth, which involves looking at the second decimal place. Since the second decimal place is 1 (which is less than 5), we round down.
It is: 21.2
326.6
62.2
14.0
8.8
It is: 276.3 because 0.02 is less than 0.05
9.4
It is: 21.2
326.6
62.2
17.2
The correct answer is 20.0
13.2 percent (rounded to 1dp).
31,600
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).