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3 years ago

75 POINTS!!! PLEASE ANSWERl

Mathematics

2 answers:

denpristay [2]3 years ago

4 0

Answer:

67th percentile

Step-by-step explanation:

If the mean is 8 with a standard deviation of 1.5, the percentile rank of a shoe with at least a size of 9 is 66.6 repeating, or 67th if rounded.

Nina [5.8K]3 years ago

4 0

Answer:

Step-by-step explanation:

Find z-score:

z = (9 - 8)/1.5 ≈ 0.67

Get the rank from the z-table:

0.7486 ≈ 75%

You might be interested in

Find the value of sin(a/2) if cosa= 12/13

daser333 [38]

Answer: sin $\frac{a}{2}$ = ± $\frac{1}{\sqrt{26} }$

Step-by-step explanation:

We very well know that,

cos2A=1−2sin²A

⟹ sinA = ± $\sqrt{(1-} \frac{cos2A}{2} )$

As required, set A = $\frac{a}{2}$ & cos a= $\frac{12}{13}$ ,thus we get

sin $\frac{a}{2}$ =± $\sqrt{\frac{1-cos a}{2} }$

∴ sin $\frac{a}{2}$ =± $\sqrt{\frac{1-\frac{12}{13} }{2} }$ = ± $\frac{1}{\sqrt{26} }$

since ,360° < $\frac{a}{2}$ <450°

,180° < $\frac{a}{2}$ <225°

Now, we are to select the value with the correct sign. It's is obvious from the above constraints that the angle a/2 lies in the III-quadrant where 'sine' has negative value, thus the required value is negative.

hope it helped!

5 0

3 years ago

X + 2y = 5 x - 3y = 7 What is the value of the y-determinant? -2 -1 2

grandymaker [24]

Answer:

y-determinant = 2

Step-by-step explanation:

Given the following system of equation:

x + 2y = 5
x - 3y = 7

Let's represent it using a matrix:

$\left[\begin{array}{ccc}1&2\\1&-3\end{array}\right] = \left[\begin{array}{ccc}5\\7\end{array}\right]$

The y‐numerator determinant is formed by taking the constant terms from the system and placing them in the y‐coefficient positions and retaining the x‐coefficients. Then:

$\left[\begin{array}{ccc}1&5\\1&7\end{array}\right]$

y-determinant = (1)(7) - (5)(1) = 2.

Therefore, the y-determinant = 2

5 0

3 years ago

I don't know if this is right... please someone help mee

worty [1.4K]

For the first circle, let's use the pythagorean theorem

$\bf \textit{using the pythagorean theorem}\\\\
c^2=a^2+b^2\implies c=\sqrt{a^2+b^2}
\qquad 
\begin{cases}
c=hypotenuse\\
a=adjacent\\
b=opposite\\
\end{cases}
\\\\\\
c=\sqrt{8^2+15^2}\implies c=\sqrt{289}\implies c=17$

now, it just so happen that the hypotenuse on that triangle, is actually 17, but we used the pythagorean theorem to find it, and the pythagorean theorem only works for right-triangles.

so if the hypotenuse is actually 17, that means that triangle there is actually a right-triangle, meaning that the radius there, and the outside line there, are both meeting at a right-angle.

when an outside line touches the radius line, and they form a right-angle, the outside line is indeed a tangent line, since the point of tangency is always a right-angle with the radius.

now, let's check for second circle

$\bf \textit{using the pythagorean theorem}\\\\
c^2=a^2+b^2\implies c=\sqrt{a^2+b^2}
\qquad 
\begin{cases}
c=hypotenuse\\
a=adjacent\\
b=opposite\\
\end{cases}
\\\\\\
c=\sqrt{11^2+14^2}\implies c=\sqrt{317}\implies c\approx 17.8044938$

well, low and behold, we didn't get our hypotenuse as 16 after all, meaning, that triangle is NOT a right-triangle, and that outside line is not touching the radius at a right-angle, therefore is NOT a tangent line.

let's check the third circle

$\bf \textit{using the pythagorean theorem}\\\\
c^2=a^2+b^2\implies c=\sqrt{a^2+b^2}
\qquad 
\begin{cases}
c=hypotenuse\\
a=adjacent\\
b=opposite\\
\end{cases}
\\\\\\
c=\sqrt{33^2+56^2}\implies c=\sqrt{4225}\implies c=\stackrel{33+32}{65}$

this time, we did get our hypotenuse to 65, the triangle is a right-triangle, so the outside line is indeed a tangent line.

6 0

3 years ago

What is a polynomial?

Wittaler [7]

An expression of more than 2 terms

6 0

3 years ago

Read 2 more answers

2. The National Safety Council routinely analyzes the benefit of seat belt use on driver safety. Their data showed that among 28

JulijaS [17]

Answer:

We conclude that there is difference in the proportion of deaths between the 2 groups.

Step-by-step explanation:

We are given that among 2823 drivers not wearing seat belts, 31 died as a result of injuries, and among 7765 drivers wearing seat belts 16 were killed.

Let $p_1$ = proportion of deaths when drivers were not wearing seat belts.

$p_2$ = proportion of deaths when drivers were wearing seat belts.

So, Null Hypothesis, $H_0$ : $p_1=p_2$ {means that there is no difference in the proportion of deaths between the 2 groups}

Alternate Hypothesis, $H_A$ : $p_1\neq p_2$ {means that there is difference in the proportion of deaths between the 2 groups}

The test statistics that would be used here Two-sample z test for proportions;

T.S. = $\frac{(\hat p_1-\hat p_2)-(p_1-p_2)}{\sqrt{\frac{\hat p_1(1-\hat p_1)}{n_1}+\frac{\hat p_2(1-\hat p_2)}{n_2} } }$ ~ N(0,1)

where, $\hat p_1$ = sample proportion of deaths when drivers were not wearing seat belts = $\frac{31}{2823}$ = 0.011

$\hat p_2$ = sample proportion of deaths when drivers were wearing seat belts = $\frac{16}{7765}$ = 0.002

$n_1$ = sample of drivers not wearing seat belts = 2823

$n_2$ = sample of drivers wearing seat belts = 7765

So, the test statistics = $\frac{(0.011-0.002)-(0)}{\sqrt{\frac{0.011(1-0.011)}{2823}+\frac{0.002(1-0.002)}{7765} } }$

= 4.438

The value of z test statistics is 4.438.

Now, at 5% significance level the z table gives critical values of -1.96 and 1.96 for two-tailed test.

Since our test statistic doesn't lie within the range of critical values of z, so we have sufficient evidence to reject our null hypothesis as it will fall in the rejection region due to which we reject our null hypothesis.

Therefore, we conclude that there is difference in the proportion of deaths between the 2 groups.

Also, Margin of error (E) = $1.96 \times \sqrt{\frac{\hat p_1(1-\hat p_1)}{n_1}+\frac{\hat p_2(1-\hat p_2)}{n_2} }$

= $1.96 \times \sqrt{\frac{0.011(1-0.011)}{2823}+\frac{0.002(1-0.002)}{7765} }$

= 0.00397

5 0

3 years ago