19c is the correct answer
1) Striangle = 1/2 * (12-8) * 4 = 1/2 * 4 * 4 = 8 km^2
2) Srectangle = 4 * 8 = 32 km^2
3) Sfigure = 8 + 32 = 40 km^2
Number C
Answer:
In order to find the variance we need to calculate first the second moment given by:
And the variance is given by:
![Var(X) = E(X^2) +[E(X)]^2 = 23.36 -[4.74]^2 = 0.8924](https://tex.z-dn.net/?f=%20Var%28X%29%20%3D%20E%28X%5E2%29%20%2B%5BE%28X%29%5D%5E2%20%3D%2023.36%20-%5B4.74%5D%5E2%20%3D%200.8924)
And the deviation would be:

Step-by-step explanation:
Previous concepts
The expected value of a random variable X is the n-th moment about zero of a probability density function f(x) if X is continuous, or the weighted average for a discrete probability distribution, if X is discrete.
The variance of a random variable X represent the spread of the possible values of the variable. The variance of X is written as Var(X).
Solution to the problem
For this case we have the following distribution given:
X 3 4 5 6
P(X) 0.07 0.4 0.25 0.28
We can calculate the mean with the following formula:

In order to find the variance we need to calculate first the second moment given by:

And the variance is given by:
![Var(X) = E(X^2) +[E(X)]^2 = 23.36 -[4.74]^2 = 0.8924](https://tex.z-dn.net/?f=%20Var%28X%29%20%3D%20E%28X%5E2%29%20%2B%5BE%28X%29%5D%5E2%20%3D%2023.36%20-%5B4.74%5D%5E2%20%3D%200.8924)
And the deviation would be:

Answer:the percentage decrease is 36.67%
Step-by-step explanation:
Initial amount of sugar in his diet is 15 spoons in a day. Currently, the amount of sugar in his diet is 9 1/2 spoons in a day. Converting to decimal, it becomes 9.5 spoon in a day. The amount by which he reduced his sugar intake is 15 - 9.5 = 5.5 spoons.
Percentage decrease would be expressed as
Amount by which the intake decreased/ initial intake × 100
It becomes
5.5/15 × 100 = 36.67%