Answer:
At least 68% of observations lie between 22 and 26 months.
Step-by-step explanation:
The Empirical Rule states that, for a normally distributed random variable:
68% of the measures are within 1 standard deviation of the mean.
95% of the measures are within 2 standard deviation of the mean.
99.7% of the measures are within 3 standard deviations of the mean.
In this problem, we have that:
Mean = 24
Standard deviation = 2
22 = 24 - 2
22 is one standard deviation below the mean
26 = 24 + 2
26 is one standard deviation above the mean.
So, by the empirical rule, at least 68% of observations lie between 22 and 26 months.
The answer is D. This is because when you take 10.65 and subtract 9.95 from it you get 0.07. If you take this number and continuously add to 9.95 you get the numbers provided in the chart. We'll also notice that the 0.07 is only added after 10 minutes of talking (10,20,30,etc.).
We have the base measurement for the triangles composing the sides. We need their altitude.
Imagine a right triangle with these sides:
(1) from the apex of the pyramid to the point on the base directly underneath it (471 ft);
(2) from the middle of base edge to the point underneath the apex (half of 708 ft = 354 ft);
(3) the hypotenuse, the altitude of a triangular side.
Using the Pythagorean Theorem, we find the hypotenuse to be
√(471^2 + 354^2) = about 589.2 feet
Now we add up the four triangles' areas. Each is base * altitude / 2, so:
4 x 708 x 589.2 / 2
= 2 x 708 x 589.2
= 834,307.2 square feet, the lateral area.
