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topjm [15]
3 years ago
15

If f(x) varies directly with x and f(x) = 40 when x = 8, find the value of f(x) when x = 2.

Mathematics
1 answer:
Mars2501 [29]3 years ago
7 0

For this case we have a direct variation of the form:

f (x) = kx

Where "k" is the constant of proportionality. To find it, we use the following data:

f (x) = 40\ and\ x = 8

Substituting:

40 = k * 8

Clearing the value of k:

k = \frac {40} {8}\\k = 5

Thus, the direct variation is given by:

f (x) = 5x

Forx = 2 we have:

f (2) = 5 * 2\\f (2) = 10

Answer:

The value of the direct variation for x = 2is: f (2) = 10


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In a process that manufactures bearings, 90% of the bearings meet a thickness specification. A shipment contains 500 bearings. A
Marina86 [1]

Answer:

(a) 0.94

(b) 0.20

(c) 90.53%

Step-by-step explanation:

From a population (Bernoulli population), 90% of the bearings meet a thickness specification, let p_1 be the probability that a bearing meets the specification.

So, p_1=0.9

Sample size, n_1=500, is large.

Let X represent the number of acceptable bearing.

Convert this to a normal distribution,

Mean: \mu_1=n_1p_1=500\times0.9=450

Variance: \sigma_1^2=n_1p_1(1-p_1)=500\times0.9\times0.1=45

\Rightarrow \sigma_1 =\sqrt{45}=6.71

(a) A shipment is acceptable if at least 440 of the 500 bearings meet the specification.

So, X\geq 440.

Here, 440 is included, so, by using the continuity correction, take x=439.5 to compute z score for the normal distribution.

z=\frac{x-\mu}{\sigma}=\frac{339.5-450}{6.71}=-1.56.

So, the probability that a given shipment is acceptable is

P(z\geq-1.56)=\int_{-1.56}^{\infty}\frac{1}{\sqrt{2\pi}}e^{\frac{-z^2}{2}}=0.94062

Hence,  the probability that a given shipment is acceptable is 0.94.

(b) We have the probability of acceptability of one shipment 0.94, which is same for each shipment, so here the number of shipments is a Binomial population.

Denote the probability od acceptance of a shipment by p_2.

p_2=0.94

The total number of shipment, i.e sample size, n_2= 300

Here, the sample size is sufficiently large to approximate it as a normal distribution, for which mean, \mu_2, and variance, \sigma_2^2.

Mean: \mu_2=n_2p_2=300\times0.94=282

Variance: \sigma_2^2=n_2p_2(1-p_2)=300\times0.94(1-0.94)=16.92

\Rightarrow \sigma_2=\sqrt(16.92}=4.11.

In this case, X>285, so, by using the continuity correction, take x=285.5 to compute z score for the normal distribution.

z=\frac{x-\mu}{\sigma}=\frac{285.5-282}{4.11}=0.85.

So, the probability that a given shipment is acceptable is

P(z\geq0.85)=\int_{0.85}^{\infty}\frac{1}{\sqrt{2\pi}}e^{\frac{-z^2}{2}=0.1977

Hence,  the probability that a given shipment is acceptable is 0.20.

(c) For the acceptance of 99% shipment of in the total shipment of 300 (sample size).

The area right to the z-score=0.99

and the area left to the z-score is 1-0.99=0.001.

For this value, the value of z-score is -3.09 (from the z-score table)

Let, \alpha be the required probability of acceptance of one shipment.

So,

-3.09=\frac{285.5-300\alpha}{\sqrt{300 \alpha(1-\alpha)}}

On solving

\alpha= 0.977896

Again, the probability of acceptance of one shipment, \alpha, depends on the probability of meeting the thickness specification of one bearing.

For this case,

The area right to the z-score=0.97790

and the area left to the z-score is 1-0.97790=0.0221.

The value of z-score is -2.01 (from the z-score table)

Let p be the probability that one bearing meets the specification. So

-2.01=\frac{439.5-500  p}{\sqrt{500 p(1-p)}}

On solving

p=0.9053

Hence, 90.53% of the bearings meet a thickness specification so that 99% of the shipments are acceptable.

8 0
3 years ago
Determine whether each pair of functions are inverse functions. 1) f(x) = 8x – 10, g(x) = (x + 10) 2) f(x) = 4x + 5, g(x) = 4x –
Y_Kistochka [10]

Answer:

Step-by-step explanation:

To find the inverse of a function you take it in y=f(x) form, switch x and y and then solve for the new y.

So I'll do the first one.

f(x) = 8x-10

y=8x-10 Now switch x and y

x = 8y-10 Now solve for y.  

x+10=8y

(x+10)/8 = y

g(x) is not that, so it is not the inverse.  Can you figure out the second one?

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3 years ago
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trapecia [35]
He would have $4131 left from $5400 with a decrease with 23.5%
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Answer:

0

Step-by-step explanation:

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8 0
2 years ago
What's the awnswer to 10 divided by 2/7?
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34.48

(2/7=.29, 10/.29=34.48)
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