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soldier1979 [14.2K]
2 years ago
13

Jillian surveyed students at her school and found out the following probabilities: P ( freshman ) = 0.30 P ( plays instrument )

= 0.20 P ( freshman and instrument ) = 0.10 ​ P(freshman)=0.30 P(plays instrument)=0.20 P(freshman and instrument)=0.10 ​ Find the probability that a student plays an instrument given they are a freshman. P ( plays instrument ∣ freshman ) =
Mathematics
1 answer:
Tatiana [17]2 years ago
6 0

Answer: 1/3

Step-by-step explanation:

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A process manufactures ball bearings with diameters that are normally distributed with mean 25.1 mm and standard deviation 0.08
marta [7]

Answer:

(a) The proportion of the diameters are less than 25.0 mm is 0.1056.

(b) The 10th percentile of the diameters is 24.99 mm.

(c) The ball bearing that has a diameter of 25.2 mm is at the 84th percentile.

(d) The proportion of the ball bearings meeting the specification is 0.8881.

Step-by-step explanation:

Let <em>X</em> = diameters of ball bearings.

The random variable <em>X</em> is normally distributed with mean, <em>μ</em> = 25.1 mm and standard deviation, <em>σ</em> = 0.08 mm.

To compute the probability of a Normally distributed random variable we need to first convert the raw scores to <em>z</em>-scores as follows:

<em>z</em> = (X - μ) ÷ σ

(a)

Compute the probability of <em>X</em> < 25.0 mm as follows:

P (X < 25.0) = P ((X - μ)/σ < (25.0-25.1)/0.08)

                    = P (Z < -1.25)

                    = 1 - P (Z < 1.25)

                    = 1 - 0.8944

                    = 0.1056

*Use a <em>z</em>-table for the probability.

Thus, the proportion of the diameters are less than 25.0 mm is 0.1056.

(b)

The 10th percentile implies that, P (X < x) = 0.10.

Compute the 10th percentile of the diameters as follows:

P (X < x) = 0.10

P ((X - μ)/σ < (x-25.1)/0.08) = 0.10

P (Z < z) = 0.10

<em>z</em> = -1.282

The value of <em>x</em> is:

z = (x - 25.1)/0.08

-1.282 = (x - 25.1)/0.08

x = 25.1 - (1.282 × 0.08)

  = 24.99744

  ≈ 24.99

Thus, the 10th percentile of the diameters is 24.99 mm.

(c)

Compute the value of P (X < 25.2) as follows:

P (X < 25.2) = P ((X - μ)/σ < (25.2-25.1)/0.08)

                    = P (Z < 1.25)

                    = 0.8944

                    ≈ 0.84

*Use a <em>z</em>-table for the probability.

Thus, the ball bearing that has a diameter of 25.2 mm is at the 84th percentile.

(d)

Compute the value of P (25.0 < X < 25.3) as follows:

P (25.0 < X < 25.3) = P ((25.0-25.1)/0.08 < (X - μ)/σ < (25.3-25.1)/0.08)

                    = P (-1.25 < Z < 2.50)

                    = P (Z < 2.50) - P (Z < -1.25)

                    = 0.99379 - 0.10565

                    = 0.88814

                    ≈ 0.8881

*Use a <em>z</em>-table for the probability.

Thus, the proportion of the ball bearings meeting the specification is 0.8881.

4 0
2 years ago
Lisa invests $4,000 in two types of bonds, bond A and bond B. Bond A offers a 10% return, and bond B offers a 6% return. Lisa in
ss7ja [257]
X+y=4000....(1)
10x+6y=340*100⇒5x+3y=17000......(2)

(2)- 3*(1)⇒ 2x=5000⇒x=2500,y=4000-2500=1500
7 0
2 years ago
Read 2 more answers
Foggy Optics, Inc., makes laboratory microscopes. Setting up each production run costs $2500. Insurance costs, based on the aver
Ray Of Light [21]

Answer: 4

Step-by-step explanation:

Let N be the total number of runs.

The microscopes per year will be equal to the total number of runs * microscopes per run

total number of microscopes = total number of runs * microscopes per run

now we have each run to cost 2500, therefore:

run costs = 2500 * total runs = 2500*N

we also have insurance and storage costs (note the average thats why we divide by 2):

storage costs = 20* microscopes per run /2 = 20*N/2

insurance costs = 15 * microscopes per run = 15*N

the costs are:

costs = run costs + storage + insurance

now the comany sells 1600 microscopes a year, so in order to figure out the number of microscopes per run we divide 1600 by the total number of runs N and replace in the costs

costs = 2500N + 40000/N => C(N) = 2500N + 40000/N

now derivate the function with respect to N and equal to 0:

\frac{d}{dN}(2500N + 40000/N) = 2500(1-16/N^2) \\\\  2500(1-16/N^2) = 0\\

this gives you two solutions, N = -4 which is not eligible (you cant make negative microscopes lol) and N = 4 which is the answer

have a nice day

4 0
2 years ago
A population of 550 rabbits is increasing by 7.5% each year. in about how many years will the population be over 1000?
Furkat [3]

I believe this would take the form of an exponential equation:

A = Ao (1 + r)^t

where A is final population, Ao is initial population, r is rate of growth and t is time

 

A / Ao = (1 + r)^t

log A / Ao = t log (1 + r)

t = (log A / Ao) / log (1 + r)

t = [log (1000 / 550)] / log (1.075)

t = 8.27 years

 

SO the answer is B) about 9 years

5 0
2 years ago
Cameras R Us has a sale for 25% off camera bags, which is a discount of $20. Explain how you can set up a diagram to find the or
Rasek [7]

Answer:

SAMPLE RESPONSE( The diagram should have five columns, one for each 25% and one for the total, because 25% is 1

4

of 100%. It should have 2 rows, 1 for percents and 1 for dollar amounts.

Step-by-step explanation:

Edg2020

8 0
2 years ago
Read 2 more answers
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