Given the mean of a random variable, X, is 10 and P(X < 11) = 0.67. Find the standard deviation.
1 answer:
Answer:
Step-by-step explanation:
This is the problem we need to solve:
and we have everything but the z-score (which we find from a table) with our main unknown being the standard deviation.
If the probability that a random variable that is less than 11 is .67, we first have to find the z-score from the table that is closest to .67, and there are 2:
P(z < .43) = .66640 and P(z < .44) = .67003
We'll use z = .44
and
and
so
σ = 2.27 (check it; it works!)
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To find this you multiply the 2 numbers together. 3*3/4=2.25.
2.25 in fraction form is
2.25 in fraction form is
Answer:
m∠ABC = 119° and DC = 105 feet
Step-by-step explanation:
For better understanding of the solution see the attached figure of the trapezium ABCD :
m∠BCD = 61°
By using the property, Sum of interior opposite angles in a trapezium is supplementary ⇒ m∠BCD + m∠ABC = 180°
⇒ m∠ABC = 180° - 61°
⇒ m∠ABC = 119°
Now, to find length of DC,
Draw a perpendicular BE on CD ⇒ CD = DE + EC
AB = DE
⇒ DE = 80 feet
In ΔBEC, By using Pythagoras theorem
EC² = BC² - BE²
⇒ EC² = 65² - 60²
⇒ EC = 25 feet
Hence, DC = 80 + 25
= 105 feet
