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3 years ago

Twice a number plus 5 equals 81

Mathematics

2 answers:

ohaa [14]3 years ago

7 0

solution

2x+5=81

2x=81-5

2x=76

x=38

Marta_Voda [28]3 years ago

7 0

Answer:

$38 = x$

Step-by-step explanation:

81 = 5 + 2x

- 5 - 5

___________

76 = 2x

__ __

2 2

$38 = x$

I am joyous to assist you anytime.

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3 years ago

Express 620 ft in yards and feet <br><br> Thanks

Kryger [21]

Answer:

around 206 yards and 2 feet

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3 years ago

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tamaranim1 [39]

Step-by-step explanation:

I used my calculator, so they should be correct.

6 0

3 years ago

Read 2 more answers

A researcher is concerned about the impact of students working while they are enrolled in classes, and she likes to know if stud

8_murik_8 [283]

Answer:

(a) Point estimate = 7.10

(b) The critical value is 1.960

(d) Confidence Interval = (6.3, 7.9)

(e) We are 90% confident that the average number of hours worked by the students is between 6.3 and 7.9

Step-by-step explanation:

Given

$\bar x = 7.10$ -- sample mean

$\sigma=5$ --- sample standard deviation

$n = 150$ --- samples

Solving (a): The point estimate

The sample mean can be used as the point estimate.

Hence, the point estimate is 7.10

Solving (b): The critical value

We have:

$CI = 90\%$ --- the confidence interval

Calculate the $\alpha$ level

$\alpha = 1 - CI$

$\alpha = 1 - 90\%$

$\alpha = 1 - 0.90$

$\alpha = 0.10$

Divide by 2

$\frac{\alpha}{2} = 0.10/2$

$\frac{\alpha}{2} = 0.05$

Subtract from 1

$1 - \frac{\alpha}{2} = 1 - 0.05$

$1 - \frac{\alpha}{2} = 0.95$

From the z table. the critical value for $1 - \frac{\alpha}{2} = 0.95$ is:

$z = 1.960$

Solving (c): Margin of error

This is calculated as:

$E = z * \frac{\sigma}{\sqrt n}$

$E = 1.960 * \frac{5}{\sqrt {150}}$

$E = 1.960 * \frac{5}{12.25}$

$E = \frac{1.960 *5}{12.25}$

$E = \frac{9.80}{12.25}$

$E = 0.800$

Solving (d): The confidence interval

This is calculated as:

$CI = (\bar x - E, \bar x + E)$

$CI = (7.10 - 0.800, 7.10 + 0.800)$

$CI = (6.3, 7.9)$

Solving (d): The conclusion

We are 90% confident that the average number of hours worked by the students is between 6.3 and 7.9

6 0

3 years ago

PLEASE:

Tju [1.3M]

Answer:

63.59 in²

Step-by-step explanation:

The formula to find the area of a square: a², where a is the side.

The formula to find the area of a circle: πr², where r is the radius (diameter ÷ 2), and the pi is alterable (3.14 or 3.142 or 22/7).

1) Find the diameter of the circle. The side of a square is the diameter.

a²

a = √81

a = 9

2) Plug the values into the formula of the area of a circle. 9 ÷ 2 = 4.5 (radius).

= 3.14 x 4.5²

= 3.14 x 20.25

= 63.585

3) Round off the result to the nearest hundredth.

= 63.59

3 0

3 years ago