Answer:
Tamara should expect the sum of the two cubes to be equal to 5 20 times.
Step-by-step explanation:
The sample space of rolling a number cube are:
S = {1, 2, 3, 4, 5, 6}
If two such cubes are rolled together, then the sum of the two cubes will be 5 for the combinations below:
S₁ = {(1, 4), (2, 3), (3, 2) and (4, 1)}
The total number of outcomes will be, <em>N</em> = 36.
Compute the probability that the sum of rolling two numbered cubes as follows:
![P(\text{Sum}=5)=\frac{4}{36}=\frac{1}{9}](https://tex.z-dn.net/?f=P%28%5Ctext%7BSum%7D%3D5%29%3D%5Cfrac%7B4%7D%7B36%7D%3D%5Cfrac%7B1%7D%7B9%7D)
Let <em>X</em> = number of time the sum of the two numbers on two cubes is 5.
Two numbered cubes are rolled <em>n</em> = 180 times.
The event of getting a sum of 5 in independent of the other results.
The random variable <em>X</em> follows a Binomial distribution with parameters <em>n</em> = 180 and <em>p</em> =
.
The expected value of <em>X</em> is:
![E(X)=np](https://tex.z-dn.net/?f=E%28X%29%3Dnp)
Compute the expected number of times Tamara expects the sum of the two cubes to be equal to 5 as follow:
![E(X)=np\\=180\times \frac{1}{9}\\=20](https://tex.z-dn.net/?f=E%28X%29%3Dnp%5C%5C%3D180%5Ctimes%20%5Cfrac%7B1%7D%7B9%7D%5C%5C%3D20)
Thus, Tamara should expect the sum of the two cubes to be equal to 5 20 times.