To cover the width we need 12÷¾=12×4/3=16 tiles.
To cover the length we need 15×4/3=20 tiles, so to cover the floor area we need 16×20=320 tiles.
Answer:


The confidence interval of standard deviation is:
to 
Step-by-step explanation:
Given

See attachment for the formatted data
Solving (a): The mean
This is calculated as:

So, we have:




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




--- approximated
Solving (c): 95% confidence interval of standard deviation
We have:

So:



Calculate the degree of freedom (df)



Determine the critical value at row
and columns
and 
So, we have:
---- at 
--- at 
So, the confidence interval of the standard deviation is:
to 
to 
to 
to 
4/6=66.67%
5/8=62.5%
Therfore 4/6 is bigger than 5/8
8.5 the answer is and replace the areas