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3 years ago

The sum of a number and 8 is 15

2 answers:

3 0

You mean, what is this number?

we can rephrase it like this: the sum of a number x and 8 is 15

which is:

x+8=15

we subtract 8 from both sides and we get
x=7

so the answer is 7.

densk [106]3 years ago

3 0

Let the missing number be known as 's'

s + 8 = 15

Subtract 8 from both sides of the equation.

s + 8 = 15
-8 -8
---------------------
s = 7.

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Find the product of (3x + 7y)(3x − 7y)

nalin [4]

Answer:

9x^2 - 49y^2

Step-by-step explanation:

7 0

3 years ago

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In a completely randomized experimental design, three brands of paper towels were tested for their ability to absorb water. Equa

arlik [135]

Answer:

Yes. At this significance level, there is evidence to support the claim that there is a difference in the ability of the brands to absorb water.

Step-by-step explanation:

The question is incomplete:

The significance level is 0.05.

The data is:

Brand X: 91, 100, 88, 89

Brand Y: 99, 96, 94, 99

Brand Z: 83, 88, 89, 76

We have to check if there is a significant difference between the absorbency rating of each brand.

Null hypothesis: all means are equal

$H_0:\mu_x=\mu_y=\mu_z$

Alternative hypothesis: the means are not equal

$H_a: \mu_x\neq\mu_y\neq\mu_z$

We have to apply a one-way ANOVA

We start by calculating the standard deviation for each brand:

$s_x^2=30,\,\,s_y^2=6,\,\,s_z^2=35.33$

Then, we calculate the mean standard error (MSE):

$MSE=(\sum s_i^2)/a=(30+6+35.33)/3=71.33/3=23.78$

Now, we calculate the mean square between (MSB), but we previously have to know the sample means and the mean of the sample means:

$M_x=92,\,\,M_y=97,\,\,M_z=84\\\\M=(92+97+84)/3=91$

The MSB is then:

$s^2=\dfrac{\sum(M_i-M)^2}{N-1}\\\\\\s^2=\dfrac{(92-91)^2+(97-91)^2+(84-91)^2}{3-1}\\\\\\s^2=\dfrac{1+36+49}{2}=\dfrac{86}{2}=43\\\\\\\\MSB=ns^2=4*43=172$

Now we calculate the F statistic as:

$F=MSB/MSE=172/23.78=7.23$

The degrees of freedom of the numerator are:

$dfn=a-1=3-1=2$

The degrees of freedom of the denominator are:

$dfd=N-a=3*4-3=12-3=9$

The P-value of F=7.23, dfn=2 and dfd=9 is:

$P-value=P(F>7.23)=0.01342$

As the P-value (0.013) is smaller than the significance level (0.05), the null hypothesis is rejected.

There is evidence to support the claim that there is a difference in the ability of the brands to absorb water.

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3 years ago

A tank 4/5 full needs 75 litres to fill it up.how many litres does it hold when full

Ann [662]

X - the volume of the tank

$\frac{4}{5}x+75=x \\
75=x-\frac{4}{5}x \\
75=\frac{1}{5}x \ \ \ |\times 5 \\
x=375$

The tank holds 375 liters when full.

8 0

3 years ago

Solve7+x/4=5 For x please show steps

seraphim [82]

7 + x/4 = 5 (common denominator is 4)

4(7+x/4) = 4 x 5 (distribute the 4 though parenthesis)

4 *7 +4x/4 = 4 x 5

4 * 7 + x = 4 x 5

28 + x = 4 x 5

28 + x = 20 (subtract the 28)

x = 20 - 28

x = -8

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tia_tia [17]

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3 years ago