Answer: It costs $5.52 to Sam to buy 12 stamps.
Step-by-step explanation:
Given: Sam paid $8.28 for 18 stamps.
Thus, the cost of 18 stamps = $8.28
Then the cost of 1 stamp=
Thus, the cost of 1 stamp=$0.46
With the same rate , the cost of 12 stamps=
Therefore, the cost of 12 stamps= $5.52
hence, it costs $5.52 to Sam to buy 12 stamps.
Answer:
And if we solve for a we got;
So the value of height that separates the bottom 95% of data from the top 5% is 11.64
Step-by-step explanation:
Previous concepts
Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".
The Z-score is "a numerical measurement used in statistics of a value's relationship to the mean (average) of a group of values, measured in terms of standard deviations from the mean".
Solution to the problem
Let X the random variable that represent certain lifetime of a population, and for this case we know the distribution for X is given by:
Where and
For this part we want to find a value a, such that we satisfy this condition:
(a)
(b)
Both conditions are equivalent on this case. We can use the z score again in order to find the value a.
As we can see on the figure attached the z value that satisfy the condition with 0.95 of the area on the left and 0.05 of the area on the right it's z=1.64. On this case P(Z<1.64)=0.95 and P(z>1.64)=0.05
If we use condition (b) from previous we have this:
But we know which value of z satisfy the previous equation so then we can do this:
And if we solve for a we got;
So the value of height that separates the bottom 95% of data from the top 5% is 11.64