Each day 1/2 the money that is in the bank vault is removed. no money is added to the vault. which of the following moddeles the situation.
i found the answer is
-exponential decay function

Exponential decay function

Step-by-step explanation:

Given: Each day 1/2 the money that is in the bank vault is removed. no money is added to the vault.

The constant ratio of decay =

A function is said to be exponential decay function if it decreases at a rate proportional to its previous value.

Here the amount in the bank is decreasing at a constant ratio of  .

Therefore, the exponential decay function models the situation.

Name m the money at the beggining of the first day. This table shows the money at the end of every day, after half the money has been removed

Day  money
1      m/2 = m/2^1
2      m/4 = m/2^2
3      m/8= m/2^3
4      m/16= m/2^4
...

n        m/2^n

The model is m/2^n, where n is numbers of days elapsed and m is the money at the end of that day (after half on the money has been removed).

The population size of the above data is 8, that is N=8
The mean (average) = (12 +10+ 11.5 +11.5 +12 +9 +9 +11)/8
                                 = 10.75
Standard deviation is the square root of variance, it is one of the measures of central dispersion, that is a measure of by how much the values in the data set are likely to differ from the mean. 
In this case, Standard deviation, s= √(∑(x-m)²)/(n-1)
                                                  = 1.172 
Thus, best approximation of the standard deviation is 1.17