Answer: The margin of error = 3.71, confidence interval = (354.04, 361.46) and it means that mean cost is lies within the confidence interval.

Step-by-step explanation:

Since we have given that

Sample size = 400

Mean = $357.75

Standard deviation = $37.89

At 95% confidence level, z = 1.96

We first find the margin of error.

Margin of error is given by

$z\times \dfrac{\sigma}{\sqrt{n}}\\\\=1.96\times \dfrac{37.89}{\sqrt{400}}\\\\=3.71$

95% confidence interval would be

$\bar{x}\pm \text{margin of error}\\\\=357.75\pm 3.71\\\\=(357.75-3.71,357.75+3.71)\\\\=(354.04,361.46)$

Hence, the margin of error = 3.71, confidence interval = (354.04, 361.46) and it means that mean cost is lies within the confidence interval.

7 0

4 years ago

An airplane is flying from New York City to Los Angeles. The distance it travels in miles d, is related to the time in seconds,

34kurt

Answer:

A. 0.15

B. 0.45

C. 85

Step-by-step explanation:

Given that:

Equation to represent the relation between distance, $d$ in miles and time $t$ in seconds:

$d=0.15t$

A.

To find: The speed of airplane in miles per second.

Formula for speed is given as:

$Speed = \dfrac{Distance}{Time}$

Here, we will have to find the value of $\frac{d}{t}$ .

Dividing the given equation by $t$ , we get:

$\dfrac{d}{t}=0.15$

$d$ is in miles and $t$ is in seconds.

Therefore, the answer is 0.15.

B.

Distance traveled in 30 seconds.

Given that: $t$ = 30 seconds

To find: $d = ?$ in miles

$d = 0.15\times 3 = 0.45$

C.

The time taken to travel a distance of 12.75 miles.

Given that : $d =12.75\ miles$

To find: $t = ?$ seconds

$12.75 = 0.15t\\\Rightarrow t = \dfrac{12.75}{0.15}\\\Rightarrow \bold{t = 85}$

3 0

3 years ago

X^2/100+y^2/25=1 The length of the major axis is:

Maru [420]

Answer:

Step-by-step explanation:

x^2/100 + y^2/25=1 -----(1)

Since 25<100

Hence the above equation is of the form x^2/a^2+ y^2/b^2=1-------(2)

Comparing (1) and (2)

a^2=100

a=10

Major axis=2a=20

5 0

4 years ago