Let the amount Tom does = x
Then Larissa’s time would be 3x( 3 times the amount of Tom)
And Neal would also be 3x
The total of the 3 is 84 hours so as an equation you have:
X + 3x + 3x = 84
Combine like terms
7x = 84
Divide both sides by 7
X = 84/7
X = 12 hours
Tom = x, so Tom exercised for 12 hours.
23 + d = 71. ———————————————————-
0, 12, 36, 108
just plug n (1,2,3,4) into the equation and that’s your answer.
Answer and Explanation:
Given : The random variable x has the following probability distribution.
To find :
a. Is this probability distribution valid? Explain and list the requirements for a valid probability distribution.
b. Calculate the expected value of x.
c. Calculate the variance of x.
d. Calculate the standard deviation of x.
Solution :
First we create the table as per requirements,
x P(x) xP(x) x² x²P(x)
0 0.25 0 0 0
1 0.20 0.20 1 0.20
2 0.15 0.3 4 0.6
3 0.30 0.9 9 2.7
4 0.10 0.4 16 1.6
∑P(x)=1 ∑xP(x)=1.8 ∑x²P(x)=5.1
a) To determine that table shows a probability distribution we add up all five probabilities if the sum is 1 then it is a valid distribution.


Yes it is a probability distribution.
b) The expected value of x is defined as

c) The variance of x is defined as

d) The standard deviation of x is defined as


