drew bought a chemistry book for $30. later that book was marked down by 20%. what was the cost of the book with the discount?
1 answer:
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Answer:
Step-by-step explanation:
Previous concepts
Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".
The Z-score is "a numerical measurement used in statistics of a value's relationship to the mean (average) of a group of values, measured in terms of standard deviations from the mean".
Solution to the problem
Let X the random variable that represent the grade points avergae of a population, and for this case we know the following properties
Where and
The empirical rule, also referred to as the three-sigma rule or 68-95-99.7 rule, is a statistical rule which states that for a normal distribution, almost all data falls within three standard deviations (denoted by σ) of the mean (denoted by µ). Broken down, the empirical rule shows that 68% falls within the first standard deviation (µ ± σ), 95% within the first two standard deviations (µ ± 2σ), and 99.7% within the first three standard deviations (µ ± 3σ).
So we can find the z score for the value of X=3.44 in order to see how many deviations above or belowe we are from the mean like this:
So the value of 3.44 is 2 deviations above from the mean, so then we know that the percentage between two deviations from the mean is 95% and on each tail we need to have (100-95)/2 = 2.5% , because the distribution is symmetrical, so based on this we can conclude that:
Answer:
<em>Martin saved $75 on the television because of the sale</em>
Step-by-step explanation:
<u>Equations</u>
Let's call x=the original price of the television (before discount).
The television had been on sale for 25% off, this means the discount was:
25% of x = = 0.25x
The sale price was the original price minus the discount:
x - 0.25x = 0.75x
This is what Martin paid, thus:
0.75x = 225
Dividing by 0.75:
x = 225 / 0.75
x = $300
The original price of the television was $300, and the discount was:
0.25*$300 = $75
Martin saved $75 on the television because of the sale