X is the radius of the slice. So we must find the equation of the side of the cone.
y=mx+b, so now we must use two points to solve for the slope, or "m".
m=(y2-y1)/(x2-x1)
m=(0-15)/(5-0)
m=-15/5
m=-3 so our line so far is:
y=-3x+b, b=y-intercept=value of y when x=0, which we can see is 15 ft so:
y=-3x+15
Now the radius is x, so we must solve for x from the equation above...
-3x+15=y subtract 15 from both sides
-3x=y-15 divide both sides by -3
x=(15-y)/3
And area of this circle is:
A=πx^2, and using x found above:
A=(π/9)(15-y)^2
A=(π/9)(225-30y+y^2), so when y=6 ft
A=(π/9)(225-30*6+6^2)
A=(π/9)(81)
A=9π or if we let π=pi
A=9pi ft^2
Answer:
(C) 4|5 -2x| > 68
Step-by-step explanation:
You can solve each of the inequalities to see if their solutions match the given numbers, or you can start with the given numbers and see what sort of inequality you end up with.
If you plot the given "solution" on a number line, you find that the numbers -6 and 11 are the same distance from x=2.5. That distance is 8.5 units. (One way to deterimine this is to average -6 and 11, then subtract that average from 11 to find the distance.
So, we can write an inequality describing values of x that are more than 8.5 units from 2.5:
|x -2.5| > 8.5
and it will have the solution x < -6 or x > 11.
Multiplying this by 2, it can become ...
|2x -5| > 17
Of course, since the absolute value function doesn't care whether its argument is positive or negative, we can also write this as ...
|5 -2x| > 17
This tells you right away which answer choice is appropriate. Further confirmation can be had by multiplying this by 4:
4|5 -2x| > 68 . . . . . . matches selection C
Answer:17
Step-by-step explanation:
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)
