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3 years ago

Out of 820 discs tested, 33 are defective. Estimate the number of defective discs in a batch of 17,000.

Mathematics

2 answers:

Zina [86]3 years ago

7 0

684 discs would be correct

Vlada [557]3 years ago

4 0

Answer:

684 discs

Step-by-step explanation:

33/820 were defective

17,000/820= 20.73

20.73*33

684 discs

-you could also do 4% of 17,000

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Solve for xxx. Write the smaller solution first, and the larger solution second.

____ [38]

Answer:

$x=-5\text{ or }x=2$

Step-by-step explanation:

We have been given an equation $x^2+3x-10=0$ . We are asked to find the solutions of our given equation.

We will use splitting the middle term method to solve quadratic equation.

We will split middle term of our given equation into parts such that whose product is $-10$ and whose sum is 3.

We know that such two numbers are $5\text{ and }-2$ .

$x^2+5x-2x-10=0$

$(x^2+5x)+(-2x-10)=0$

$x(x+5)-2(x+5)=0$

$(x+5)(x-2)=0$

Using zero product property, we will get:

$(x+5)=0\text{ or }(x-2)=0$

$x+5=0\text{ or }x-2=0$

$x=-5\text{ or }x=2$

Therefore, the solutions for our given equation are $x=-5\text{ or }x=2$ .

4 0

3 years ago

Read 2 more answers

Which product is greater than 3/4?

kenny6666 [7]

Answer:

first one

Step-by-step explanation:

all the others are lower than 3/4 or .75

6 0

3 years ago

You want to obtain a sample to estimate a population mean. Based on previous evidence, you believe the population standard devia

Arturiano [62]

Answer:

$n=(\frac{z_{\alpha/2} \sigma}{ME})^2$ (3)

$n=(\frac{2.58(54.5)}{5})^2 =790.846 \approx 791$

So the answer for this case would be n=791 rounded up to the nearest integer

Step-by-step explanation:

Previous concepts

A confidence interval is "a range of values that’s likely to include a population value with a certain degree of confidence. It is often expressed a % whereby a population means lies between an upper and lower interval".

The margin of error is the range of values below and above the sample statistic in a confidence interval.

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".

$\bar X$ represent the sample mean for the sample

$\mu$ population mean (variable of interest)

s represent the sample standard deviation

n represent the sample size

Solution to the problem

The confidence interval for the mean is given by the following formula:

$\bar X \pm z_{\alpha/2}\frac{\sigma}{\sqrt{n}}$ (1)

Since the Confidence is 0.99 or 99%, the value of $\alpha=0.01$ and $\alpha/2 =0.005$ , and we can use excel, a calculator or a table to find the critical value. The excel command would be: "=-NORM.INV(0.005,0,1)".And we see that $z_{\alpha/2}=2.58$