I believe it's B.
If I'm wrong tell me so I can see what I did wrong.
Just solve until the answers are the same
25 times x plus 30 for John
15 times x plus 50 for Mary
Complete question:
The manager of a supermarket would like to determine the amount of time that customers wait in a check-out line. He randomly selects 45 customers and records the amount of time from the moment they stand in the back of a line until the moment the cashier scans their first item. He calculates the mean and standard deviation of this sample to be barx = 4.2 minutes and s = 2.0 minutes. If appropriate, find a 90% confidence interval for the true mean time (in minutes) that customers at this supermarket wait in a check-out line
Answer:
(3.699, 4.701)
Step-by-step explanation:
Given:
Sample size, n = 45
Sample mean, x' = 4.2
Standard deviation
= 2.0
Required:
Find a 90% CI for true mean time
First find standard error using the formula:




Standard error = 0.298
Degrees of freedom, df = n - 1 = 45 - 1 = 44
To find t at 90% CI,df = 44:
Level of Significance α= 100% - 90% = 10% = 0.10

Find margin of error using the formula:
M.E = S.E * t
M.E = 0.298 * 1.6802
M.E = 0.500938 ≈ 0.5009
Margin of error = 0.5009
Thus, 90% CI = sample mean ± Margin of error
Lower limit = 4.2 - 0.5009 = 3.699
Upper limit = 4.2 + 0.5009 = 4.7009 ≈ 4.701
Confidence Interval = (3.699, 4.701)
Answer:
A) 1/45
B) 1/60
Step-by-step explanation:
<u>Part A</u>
The actual car has a length to width ratio of ...
length/width = (570 cm)/(180 cm) = 57/18 = 3 1/6
The rectangle on the screen has a length to width ratio of ...
length/width = (13 cm)/(4 cm) = 3 1/4
Relative to its width, the screen rectangle is longer than necessary for a model of the car. So, the scale factor will be determined by the width of the car relative to the width of the screen model.
For a model width of 4 cm, the scale factor is ...
model/life-size = (4 cm)/(180 cm) = 1/45
__
<u>Part B</u>
For a model width of 3 cm, the scale factor is ...
model/life-size = (3 cm)/(180 cm) = 1/60
I think its 14 because in order to get to 28 but 2 you count 14 times saying 2×14