The average marks of the first 10 students are 17 and that of the next 15 students is 18. find the mean of 25 students?
1 answer:
Answer:
The mean of 25 students is 17.6
Step-by-step explanation:
The formula of the mean (average) is mean (average) = , where S is the sum of the data, and N is the number of the data
∵ The average marks of the first 10 students are 17
- That means the mean is 17 and the number of students is 10
∴ Average = 17
∴ N = 10
∵ Average =
- Substitute average by 17 and N by 10
∴ 17 =
- Multiply both sides by 10
∴ 170 = S
∴ The sum of the marks of the first 10 students is 170
∵ The average of the next 15 students is 18
∴ Average = 18
∴ N = 15
- Substitute average by 18 and N by 15
∴ 18 =
- Multiply both sides by 15
∴ 270 = S
∴ The sum of the marks of the next 15 students is 270
Now to find the mean of 25 students and the two sums and divide the answer by 25
∵ S = 170 + 270
∴ S = 440
∵ N = 25
∴ Mean =
∴ Mean = 17.6
The mean of 25 students is 17.6
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Answer:
(a) The expected value and standard deviation of the amount of ice cream served at the party are 54 ounces and 1.25 ounces respectively.
(b) The expected value and standard deviation of the amount of ice cream left in the box after scooping out one scoop are 46 ounces and 1.031 ounces respectively.
(c) Because the variance of each variable is dependent on the other.
Step-by-step explanation:
The random variable <em>X</em> and <em>Y</em> are defined as follows:
<em>X</em> = amount of ice cream in the box
<em>Y</em> = amount of ice cream scooped out
The information provided is:
E (X) = 48
SD (X) = 1
V (X) = 1
E (Y) = 2
SD (Y) = 0.25
V (Y) = 0.0625
(a)
The total amount of ice-cream served at the party can be expressed as:
<em>X</em> + 3<em>Y</em>.
Compute the expected value of (<em>X</em> + 3<em>Y</em>) as follows:
Compute the variance of (<em>X</em> + 3<em>Y</em>) as follows:
Then the standard deviation of (<em>X</em> + 3<em>Y</em>) is:
Thus, the expected value and standard deviation of the amount of ice cream served at the party are 54 ounces and 1.25 ounces respectively.
(b)
The amount of ice-cream left in the box after scooping out one scoop is represented as follows:
<em>X</em> - <em>Y</em>.
Compute the expected value of (<em>X</em> - <em>Y</em>) as follows:
Compute the variance of (<em>X</em> - <em>Y</em>) as follows:
Then the standard deviation of (<em>X</em> - <em>Y</em>) is:
Thus, the expected value and standard deviation of the amount of ice cream left in the box after scooping out one scoop are 46 ounces and 1.031 ounces respectively.
(c)
The variance of the sum or difference of two variables is computed by adding the individual variances. This is because the variance of each variable is dependent on the others.
Answer:
B. Place the compass at P and draw an arc of length OP across the circle.
Below is the diagram for help.
Step-by-step explanation:
We are given with an already constructed circle of diameter and
as radius.
To draw a regular hexagon(six-sided), we need to make first cut on the circle of an arc equal to radius of the circle taking any point of the diameter as center
So here, We will consider as a center and take an arc of length
and make a cut on the circle.
This would be the first step and James need to repeat the same steps by considering the newly formed cut as center each time.
