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olga_2 [115]
3 years ago
12

zack bought a coat for $ 69.78 he paid with a $100 bill and received $26.73 in change. how much was the sales tax ?

Mathematics
1 answer:
Ratling [72]3 years ago
5 0

The sales tax was $3.49.

First, you just subtract 69.78 from 100, and you get 30.22. Then you subtract 26.73 from 30.22 and you get 3.49.

Hope that helped!

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An automobile dealer wants to see if there is a relationship between monthly sales and the interest rate. A random sample of 4 m
SVETLANKA909090 [29]

Answer:

a) y=-6.254 x +75.064  

b) r =-0.932

The % of variation is given by the determination coefficient given by r^2 and on this case -0.932^2 =0.8687, so then the % of variation explained by the linear model is 86.87%.

Step-by-step explanation:

Assuming the following dataset:

Monthly Sales (Y)     Interest Rate (X)

       22                               9.2

       20                               7.6

       10                                10.4

       45                                5.3

Part a

And we want a linear model on this way y=mx+b, where m represent the slope and b the intercept. In order to find the slope we have this formula:

m=\frac{S_{xy}}{S_{xx}}  

Where:  

S_{xy}=\sum_{i=1}^n x_i y_i -\frac{(\sum_{i=1}^n x_i)(\sum_{i=1}^n y_i)}{n}  

S_{xx}=\sum_{i=1}^n x^2_i -\frac{(\sum_{i=1}^n x_i)^2}{n}  

With these we can find the sums:  

S_{xx}=\sum_{i=1}^n x^2_i -\frac{(\sum_{i=1}^n x_i)^2}{n}=278.65-\frac{32.5^2}{4}=14.5875  

S_{xy}=\sum_{i=1}^n x_i y_i -\frac{(\sum_{i=1}^n x_i)(\sum_{i=1}^n y_i){n}}=696.9-\frac{32.5*97}{4}=-91.225  

And the slope would be:  

m=\frac{-91.225}{14.5875}=-6.254  

Nowe we can find the means for x and y like this:  

\bar x= \frac{\sum x_i}{n}=\frac{32.5}{4}=8.125  

\bar y= \frac{\sum y_i}{n}=\frac{97}{4}=24.25  

And we can find the intercept using this:  

b=\bar y -m \bar x=24.25-(-6.254*8.125)=75.064  

So the line would be given by:  

y=-6.254 x +75.064  

Part b

For this case we need to calculate the correlation coefficient given by:

r=\frac{n(\sum xy)-(\sum x)(\sum y)}{\sqrt{[n\sum x^2 -(\sum x)^2][n\sum y^2 -(\sum y)^2]}}  

r=\frac{4(696.9)-(32.5)(97)}{\sqrt{[4(278.65) -(32.5)^2][4(3009) -(97)^2]}}=-0.937  

So then the correlation coefficient would be r =-0.932

The % of variation is given by the determination coefficient given by r^2 and on this case -0.932^2 =0.8687, so then the % of variation explained by the linear model is 86.87%.

6 0
3 years ago
Solve for a: a(a-3) =100
marissa [1.9K]
a(a-3) =100\\
a^2-3a-100=0\\
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\sqrt{\Delta}=\sqr{409}\\
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a_2=\dfrac{-(-3)+\sqrt{409}}{2\cdot1}=\dfrac{3+\sqrt{409}}{2}
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In a certain country, the car number plate is formed by 4 digits from the digits 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9 followed by 2 l
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