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2 years ago

Mr. Jones grades 12 exams

Mathematics

2 answers:

aniked [119]2 years ago

5 0

Answer:

8 hours

Step-by-step explanation:

12/2= 6
He grades 6 exams per hour
48/6= 8
it would take 8 hours to grade 48 exams

Bonus:
it takes him 10 minutes to grade an exam. That doesnt matter for this question but it's good 2 know

Ad libitum [116K]2 years ago

3 0

Answer:

8 hours

Step-by-step explanation:

To solve this it seems you need to set up a proportion.

12/2=48/x

cross multiply the 2 and 48.

2•48=96.

divide by the remaining number to get x.

96/12=8.

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Answer:

x + y = 20
20x +30y = 450

Step-by-step explanation:

The equation for the total number of cases is ...

x + y = 20

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Additional comment

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2 years ago

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I think it’s (-1,-4) sorry if it’s wrong

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2 years ago

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Evaluate the expression below when x = -2. x2 − 8 x + 6

nordsb [41]

Solve for x over the real numbers:x = -2. x^2 - 8 x + 6
Hint: | Rewrite the right hand side of the equation.-2. x^2 - 8 x + 6 = -2 x^2 - 8 x + 6:x = -2 x^2 - 8 x + 6
Hint: | Move everything to the left hand side.Subtract -2 x^2 - 8 x + 6 from both sides:2 x^2 + 9 x - 6 = 0
Hint: | Write the quadratic equation in standard form.Divide both sides by 2:x^2 + (9 x)/2 - 3 = 0
Hint: | Solve the quadratic equation by completing the square.Add 3 to both sides:x^2 + (9 x)/2 = 3
Hint: | Take one half of the coefficient of x and square it, then add it to both sides.Add 81/16 to both sides:x^2 + (9 x)/2 + 81/16 = 129/16
Hint: | Factor the left hand side.Write the left hand side as a square:(x + 9/4)^2 = 129/16
Hint: | Eliminate the exponent on the left hand side.Take the square root of both sides:x + 9/4 = sqrt(129)/4 or x + 9/4 = -sqrt(129)/4
Hint: | Look at the first equation: Solve for x.Subtract 9/4 from both sides:x = sqrt(129)/4 - 9/4 or x + 9/4 = -sqrt(129)/4
Hint: | Look at the second equation: Solve for x.Subtract 9/4 from both sides:Answer: x = sqrt(129)/4 - 9/4 or x = -9/4 - sqrt(129)/4

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3 years ago

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A group of friends are playing golf. The total cost of the round of golf is $108. Each person in the group has the same coupon.

marta [7]

For this equation, we can let c = the value of one coupon
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Hope this helped, and if it did I'd appreciate if you marked me as brainliest as I need it to get to a higher rank. If you need any more help, feel free to add me and/or message me :)

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3 years ago

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Listed below are systolic blood pressure measurements (mm Hg) taken from the right and left arms of the same woman. Consider the

Dafna1 [17]

Answer:

a) $\bar d= \frac{\sum_{i=1}^n d_i}{n}=72.2$

$s_d =\sqrt{\frac{\sum_{i=1}^n (d_i -\bar d)^2}{n-1}} =9.311$

b) The 90% confidence interval would be given by (63.330;81.070)

$63.330 < \mu_{left}- \mu_{right}$

Step-by-step explanation:

1) Previous concepts and notation

A confidence interval is "a range of values that’s likely to include a population value with a certain degree of confidence. It is often expressed a % whereby a population means lies between an upper and lower interval".

The margin of error is the range of values below and above the sample statistic in a confidence interval.

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".

Let put some notation

x=left arm , y = right arm

x: 175 169 182 146 144

y: 102 101 94 79 79

The first step is define the difference $d_i=x_i-y_i$ , that is given so we have:

d: 73, 68, 88, 67, 65

The second step is calculate the mean difference

$\bar d= \frac{\sum_{i=1}^n d_i}{n}=72.2$

The third step would be calculate the standard deviation for the differences, and we got:

$s_d =\sqrt{\frac{\sum_{i=1}^n (d_i -\bar d)^2}{n-1}} =9.311$

2) Confidence interval

The confidence interval for the mean is given by the following formula:

$\bar d \pm t_{\alpha/2}\frac{s_d}{\sqrt{n}}$ (1)

In order to calculate the critical value $t_{\alpha/2}$ we need to find first the degrees of freedom, given by:

$df=n-1=5-1=4$

Since the Confidence is 0.90 or 90%, the value of $\alpha=0.1$ and $\alpha/2 =0.05$ , and we can use excel, a calculator or a table to find the critical value. The excel command would be: "=-T.INV(0.05,4)".And we see that $t_{\alpha/2}=2.13$

Now we have everything in order to replace into formula (1):

$72.2-2.13\frac{9.311}{\sqrt{5}}=63.330$

$72.2+2.13\frac{9.311}{\sqrt{5}}=81.070$

So on this case the 90% confidence interval would be given by (63.330;81.070)

$63.330 < \mu_{left}- \mu_{right}$

3 0

2 years ago