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Answer:
The 95% confidence interval for the average monthly electricity consumed units is between 47.07 and 733.87
Step-by-step explanation:
We have the standard deviation for the sample. So we use the t-distribution to solve this question.
The first step to solve this problem is finding how many degrees of freedom, we have. This is the sample size subtracted by 1. So
df = 45 - 1 = 44
95% confidence interval
Now, we have to find a value of T, which is found looking at the t table, with 44 degrees of freedom(y-axis) and a confidence level of . So we have T = 2.0141
The margin of error is:
M = T*s = 2.0141*170.5 = 343.4
In which s is the standard deviation of the sample.
The lower end of the interval is the sample mean subtracted by M. So it is 390.47 - 343.40 = 47.07 units per month
The upper end of the interval is the sample mean added to M. So it is 390.47 + 343.40 = 733.87 units per month
The 95% confidence interval for the average monthly electricity consumed units is between 47.07 and 733.87
Answer:
1 cake and 6 pies
Step-by-step explanation:
Let c represent the number of cakes Alice and George can make. Likewise, let p represent the number of pies.
Then the amount of flour they need (in cups) is ...
3c + 2p . . . . cups of flour needed
And the amount of sugar needed is ...
2c + 1.5p . . . cups of sugar needed
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They want to use all 15 cups of flour they have, and all 11 cups of sugar, so the amounts above need to match the amounts on hand:
3c + 2p = 15
2c + 1.5p = 11
We can solve these equations various ways. One of my favorite is to use a graphing calculator. (See attached) It tells us that Alice and George can make 1 cake and 6 pies with the flour and sugar they have.
_____
If you want to solve these equations algebraically, there are several methods for that, too. Here, we can multiply the first one by 2/3 and subtract the result from the second one:
(2c +1.5p) -(2/3)(3c +2p) = (11) -(2/3)(15)
2c +3/2p -2c -4/3p = 11 -10 . . . . . eliminate parentheses
1/6p = 1 . . . . . . . . . . . . . . . . . . . . . .collect terms
p = 6 . . . . . . . . . . . . . . . . . . . . . . . . multiply by 6
Substituting into the first equation gives ...
3c +2·6 = 15 . . . substitute 6 for p
3c = 3 . . . . . . . . subtract 12
c = 1 . . . . . . . . . . divide by 3
These values tell us Alice and George can make 1 cake and 6 pies with the flour and sugar they have.
