Well you find how much the error was and divide it by the amount he predicted.
30/230= 0.13 0.13=13%
Add up the fractional amounts and divide them by however many amounts there are..........
eg.
Step 1:Add the fractions
1/6 + 5/8 +3/4
(find the LCD)
1/6 + 5/8 + 3/4 = 4/24 + 15/24 + 18/24 = 37/24
Step 2: Divide the sum by the number of numbers in the set
37/24 ÷ 3= 37/24 ÷ 3/1= 37/24 X 1/3= 37/72
<span>So the mean (average) is 37/72</span>
.......................................
D.) 2cm, 12cm, 16cm
'cause the sum of two small sides must be greater than that of longest side.
Hope this helps!