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3 years ago

35% of 20kids are boys.How many boys are there?

Mathematics

2 answers:

lesya [120]3 years ago

8 0

35% of 20 = 35/100 × 20 = 7 boys
pls mark brainliest

Mama L [17]3 years ago

5 0

The answer is 7. 20 times .35 is 7

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3. A new process has been developed for applying pho toresist to 125-mm silicon wafers used in manufac turing integrated circu

dlinn [17]

Answer:

The null hypothesis is $H_o : \mu = 13.4000$

The alternative hypothesis is $H_a : \mu \ne 13.4000$

The null hypothesis is rejected

The 99% confidence level is $13.3930 < \mu < 13.3994$

Step-by-step explanation:

From the question we are told that

The sample size is n = 10

The population mean is $\mu = 13.4 000 \ angstroms$

The level of significance is $\alpha = 0.05$

The sample data is

13.3987, 13.3957, 13.3902, 13.4015, 13.4001, 13.3918, 13.3965, 13.3925, 13.3946, and 13.4002

Generally the sample mean is mathematically represented as

$\= x = \frac{13.3987+ 13.3957\cdots +13.4002 }{10}$

=> $\= x = 13.3962$

Generally the sample standard deviation is mathematically represented as

$\sigma = \sqrt{\frac{\sum (x_i - \= x)^2}{n} }$

=> $\sigma = \sqrt{\frac{ (13.3987 - 13.3962)^2 + (13.3987 - 13.3962)^2 + \cdots + (13.3987 -13.4002)^2 }{10} }$

=> $\sigma =0.0039$

The null hypothesis is $H_o : \mu = 13.4000$

The alternative hypothesis is $H_a : \mu \ne 13.4000$

Generally the test statistics is mathematically represented as

$z = \frac{\= x - \mu}{\frac{\sigma}{\sqrt{n} } }$

=> $z = \frac{13.3962 - 13.4000}{\frac{0.0039}{\sqrt{10} } }$

=> $z = 3.08$

Generally the p-value is mathematically represented as

$p-value = 2P( z > 3.08)$

From the z-table $P(z > 3.08)= 0.001035$

$p-value = 2* 0.001035$

$p-value = 0.00207$

So from the obtained value we see that

$p-value < \alpha$

Hence the null hypothesis is rejected

Consider the b question

Given that the confidence level is 99% then the level of significance is

$\alpha = (100 -99)\%$

=> $\alpha = 0.01$

Generally from the normal distribution table critical value of $\frac{\alpha }{2}$ is

$Z_{\frac{\alpha }{2} } = 2.58$

Generally the margin of error is mathematically represented as

$E = Z_{\frac{\alpha }{2} } * \frac{\sigma}{\sqrt{n} }$

=> $E = 2.58 * \frac{0.0039}{\sqrt{10} }$

=> $E = 0.00318$

Generally the 99% confidence interval is mathematically represented as

$13.3962 - 0.00318 < \mu < 13.3962 + 0.00318$

=> $13.3930 < \mu < 13.3994$

7 0

3 years ago

Two trains left the station traveling in opposite directions. The distance Train A traveled is modeled by the function d(t)=81t

stira [4]

Answer:

Option A - The distance Train A traveled in 1 h is equal to the distance Train B traveled in 1 h.

Step-by-step explanation:

Given : The distance Train A traveled is modeled by the function $d(t)=81t$

where d represents distance in miles and t represents time in hours.

To find : How does the distance Train A traveled in 1 hour compare to the distance Train B traveled in 1 hour?

Solution :

Distance traveled by Train A in 1 hour is

$d(t)=81t$

$d(t)=81(1)=81$

Distance traveled by Train B in 1 hour is

$d(t)=81t$

$d(t)=81(1)=81$

or for B, we have 324 miles in 4 hours. If that is at a constant speed, it travels 324/4 = 81 miles in one hour

Therefore, The distance Train A traveled in 1 h is equal to the distance Train B traveled in 1 h.

Hence, Option A is correct.

8 0

3 years ago

Two mechanics work on a car . The first mechanic worked 10 hours and the second mechanic worked for 15 hours. Together they char

bonufazy [111]

Answer:

110

Step-by-step explanation:

Let x = rate #1 and then 155-x=rate #2.

15x + 5(155-x) = 1225

15x - 5x + 775 - 1225

10x = 450

x = 45, second rate is 110

8 0

3 years ago

Read 2 more answers

How many numbers between 19 and 79 are the prouducts of two even numbers?

Deffense [45]

The answer is 15 (brainly is omd)

7 0

2 years ago

Number of band members beyerhighschool in Orange County

makvit [3.9K]

Answer:

its answer is in high school is ten

8 0

3 years ago