<span>Cross multiply:
2 * n = 5 * 12
Simplifying
2 * n = 5 * 12
Multiply 5 * 12
2n = 60
Solving
2n = 60
Solving for variable 'n'.
Move all terms containing n to the left, all other terms to the right.
Divide each side by '2'.
n = 30
Simplifying
n = 30</span>
4 hours and 15 minutes =4+15/60=4.25 hours
the average speed of the train = 250/4.25=58.82mph
Answer:
yes
Step-by-step explanation:
Complete Question
A civil engineer is analyzing the compressive strength of concrete. Compressive strength is normally distributed with
. A random sample of 12 sample specimens has a mean compressive strength of 
. Round your answers to 1 decimal place. (a) Calculate the 95% two-sided confidence interval on the true mean compressive strength of concrete.
Answer:
Step-by-step explanation:
From the question we are told that:
Sample size 
Standard deviation 
Sample mean 
Confidence level =95%
significance level
From table \alpha 0.05
Gives
Generally the equation for confidence interval is mathematically given by
If <em>θ</em> lies in the fourth quadrant, then sin(<em>θ</em>) < 0 and cos(<em>θ</em>) > 0. So we have from the Pythagorean identity,
sin²(<em>θ</em>) + cos²(<em>θ</em>) = 1 ==> cos(<em>θ</em>) = +√(1 - sin²(<em>θ</em>)) = √21/5
Then
sec(<em>θ</em>) = 1/cos(<em>θ</em>) = 5/√21
and
tan(<em>θ</em>) = sin(<em>θ</em>)/cos(<em>θ</em>) = (-2/5)/(√21/5) = -2/√21
