Answer:
12.686cm
Step-by-step explanation:
By using pythagoras, we can find CB.
We know that 
Therefore, 
(it has to be positive since it is distance)
now we look at triangle BCD and use SOH CAH TOA.

To find the mean you add all the numbers then divide by how many numbers there are :
8+16+12+11+8=55
in the equation there are 5 numbers, so you divide 55 by 5 :
55÷5=11
the mean is 11
hope this helps
Answer:


Step-by-step explanation:
Given


Solving (a): The mean
This is calculated as:

So, we have:



Solving (b): The standard deviation
This is calculated as:

So, we have:



