What is the solution to the inequality?<br>10.2 +18

The sum of the first 3 terms of a geometric series is 171 and the common ratio is 2/3

Nimfa-mama [501]

<h3>Answer: 81</h3>

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Work Shown:

a = first term

a*(2/3) = (2/3)a= second term

(2/3)a*(2/3) = (4/9)a = third term

note how I multiplied each previous term by the common ratio (2/3) to get the next term

Add up the three terms

a + (2/3)a + (4/9)a = (9/9)a + (6/9)a + (4/9)a = (19/9)a

Set this equal to 171, which is what we want the first three terms to sum to, then solve for 'a'

(19/9)a = 171

a = (9/19)*171

a = 81 is the first term

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Checking the answer:

a = 81 = first term

(2/3)*a = (2/3)*81 = 54 = second term

(4/9)*a = (4/9)*81 = 36 = third term

adding up the three terms gets us

81+54+36 = 171

so we have confirmed the answer

4 0

2 years ago

A paper describes a study in which researchers observed wait times in coffee shops in Boston. Both wait time and gender of the c

kvasek [131]

Answer:

$t=\frac{85.8-113.4}{\sqrt{\frac{(50)^2}{145}+\frac{(75)^2}{141}}}}=-3.65$

$p_v =2*P(t_{(284)}$

Using Excel we can use the following code: "=2*T.DIST(-3.65;284;TRUE)"

So the p value is a very low value and using any significance level giveen $\alpha=0.05$ always $p_v$ so we can conclude that we have enough evidence to reject the null hypothesis, and there is enough evidence to conclude that the means are different.

Step-by-step explanation:

1) Data given and notation

$\bar X_{M}=85.8$ represent the mean for the males

$\bar X_{F}=113.4$ represent the mean for females

$s_{M}=50$ represent the sample standard deviation for males

$s_{F}=75$ represent the sample standard deviation for female

$n_{M}=145$ sample size for the group poisoned

$n_{F}=141$ sample size for the group unpoisoned

t would represent the statistic (variable of interest)

2) Concepts and formulas to use

We need to conduct a hypothesis in order to check if the mean for the two groups are equal or not , the system of hypothesis would be:

Null hypothesis: $\mu_{M} = \mu_{F}$

Alternative hypothesis: $\mu_{M} \neq \mu_{F}$

If we analyze the size for the samples both are higher than 30 but the population deviations are not given, so for this case is better apply a t test to compare means, and the statistic is given by:

$t=\frac{\bar X_{M}-\bar X_{F}}{\sqrt{\frac{s^2_{M}}{n_{M}}+\frac{s^2_{F}}{n_{F}}}}$ (1)

t-test: Is used to compare group means. Is one of the most common tests and is used to determine whether the means of two groups are equal to each other.

3) Calculate the statistic

We can replace in formula (1) the results obtained like this:

$t=\frac{85.8-113.4}{\sqrt{\frac{(50)^2}{145}+\frac{(75)^2}{141}}}}=-3.65$

4) Statistical decision

The first step is calculate the degrees of freedom, on this case:

$df=n_{M}+n_{F}-2=145+141-2=284$

Since is a two tailed test the p value would be:

$p_v =2*P(t_{(284)}$

Using Excel we can use the following code: "=2*T.DIST(-3.65;284;TRUE)"

So the p value is a very low value and using any significance level giveen $\alpha=0.05$ always $p_v$ so we can conclude that we have enough evidence to reject the null hypothesis, and there is enough evidence to conclude that the means are different.

4 0

3 years ago

What is -5 3/4 - 3 1/2

lubasha [3.4K]

Simplify the expression.

Exact Form:

−37/4

Decimal Form:

−9.25

Mixed Number Form:

−9 1/4

3 0

3 years ago

Read 2 more answers

Given a regular decagon, find the measures of the angles formed by (

Sonja [21]

A decagon has 10 sides (think decade and decathlon). From the center of the decagon we draw the radii and in doing so we take the area of the decagon and divide it into 10 congruent Triangles.

The angles around the center add up to 360 because they form a circle and since there are 10, they each measure 36 degrees. So the answer to the first part (the angle between the radii) is 36 degrees.

Each of these triangles has two equal sides (both radii) so is Isosceles. That means that the base angles are congruent. So the two angles that are left in each triangle must measure the same. Since the angles in a triangle add up to 180 degrees, we know that the two remaining angles are together equal to 180-36=144 degrees. Since they are equal in measure they each measure 72 degrees.

Thus the answer to the second part, trhe measure of the angle between a radius and the side of the polygon is 72 degrees.

3 0

3 years ago

Factories <br>(a+b)^3+8c^3

Rom4ik [11]

Answer:

(a + b + 2c)(a² + 2ab + b² - 2ac - 2bc + 4c²)

Step-by-step explanation:

Given

(a + b)³ + 8c³ ← this is a sum of cubes and factors in general as

a³ + b³ = (a + b)(a² - ab + b²)

Thus

(a + b)³ + 8c³

= (a + b)³ + (2c)³

= (a + b + 2c)( (a + b)² - 2c(a + b) + (2c)² )

= (a + b + 2c)(a² + 2ab + b² - 2ac - 2bc + 4c²)

8 0

3 years ago

What is the solution to the inequality?10.2 +18 < -2​

What is the solution to the inequality?10.2 +18 < -2