1/21 * 1/20 = 1/420 that is the probability that you are chosen first.
Probability of your friend chosen first = 1/420 also.
So the required probability = 1/420 + 1/420 = 1/210 Answer
Its D
Given Information:
Number of lithium batteries = n = 16
Mean life of lithium batteries = μ = 645 hours
Standard deviation of lithium batteries = σ = 31 hours
Confidence level = 95%
Required Information:
Confidence Interval = ?
Answer:

Step-by-step explanation:
The confidence interval is given by

Where μ is the mean life of lithium batteries, σ is the standard deviation, n is number of lithium batteries selected, and t is the critical value from the t-table with significance level of
tα/2 = (1 - 0.95) = 0.05/2 = 0.025
and the degree of freedom is
DoF = n - 1 = 16 - 1 = 15
The critical value (tα/2) at 15 DoF is equal to 2.131 (from the t-table)





Therefore, the 95% confidence interval is 628.5 to 661.5 hours
What does it mean?
It means that we are 95% confident that the mean life of 16 lithium batteries is within the interval of (628.5 to 661.5 hours)
Answer:
I believe its -7/5 unless they want -7/-5
Step-by-step explanation:
(4,3) (-1,-4)
X1,y1 x2,y2
And it should be
Y2-y1
X2-x1
-4-3 = -7
Over
-1-4 = -5
So -7/5 or -7/-5 whatever your teacher perfers
Hope this helps
Answer:
Part 1) The cost per second is 
Part 2) The cost per customer is 
Step-by-step explanation:
Part 1) Calculate the cost per second
we know that
To find out the cost per second, divide the total cost by the time
Let
x ----> the total cost
y ----> the time in seconds
we have



therefore
The cost per second is 
Part 2) Calculate the cost per customer
we know that
To find out the cost per customer, divide the total cost by the number of customers
Let
x ----> the total cost
y ----> the number of customers
we have



therefore
The cost per customer is 
Answer:
Substitute 3x - 5 for y in the second equation.
Step-by-step explanation:
Generally, to solve the system of linear equations of x and y, the first step would be trying to eliminate x (or y).
Then turn the system into the equation of only y (or x).
Next, try to solve for y (or x).
Then substitute the solved y (or x) into the original system to work out x (or y).
**********
3 options (1 addition, 2 subtractions) do not eliminate x or y (x and y still exist after manipulation).
=> Remaining option relating substitution would be a reasonable choice.