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3 years ago

ASAP:::::: 75 POINTS TO THE BRAINLIEST!!!!!

Mathematics

1 answer:

Misha Larkins [42]3 years ago

6 0

Answer:

t = 6 4/25 hours

Step-by-step explanation:

The formula to find out how long it takes them to do the job is

1/m + 1/ a = 1 /t

where m is the time for Matthew to do the job

a is the time for Arianna to do the job

and t is the time for them to do the job together

m = 14 hours

a = 11 hours

Substituting what we know

1/14 + 1/11 = 1/t

Multiplying by 154t (14*11*t) so we can clear the fractions

154t*(1/14 + 1/11) = 1/t* 154t

11t + 14t = 154

Combine like terms

25t = 154

Divide by 25

t = 154/25

t = 6 4/25 hours

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The manager of a grocery store has taken a random sample of 100 customers. The average length of time it took these 100 customer

AlladinOne [14]

Answer:

$4-2.326\frac{1}{\sqrt{100}}=3.767$

$4+2.326\frac{1}{\sqrt{100}}=4.233$

So on this case the 98% confidence interval would be given by (3.767;4.233)

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".

$\bar X=4$ represent the sample mean

$\mu$ population mean (variable of interest)

$\sigma=1$ represent the population standard deviation

n=100 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 0.98 or 98%, the value of $\alpha=0.02$ and $\alpha/2 =0.01$ , and we can use excel, a calculator or a table to find the critical value. The excel command would be: "=-NORM.INV(0.01,0,1)".And we see that $z_{\alpha/2}=2.326$

Now we have everything in order to replace into formula (1):

$4-2.326\frac{1}{\sqrt{100}}=3.767$

$4+2.326\frac{1}{\sqrt{100}}=4.233$

So on this case the 98% confidence interval would be given by (3.767;4.233)

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3 years ago

Renita started her homework at 3:45 P.M. She worked for 2 hours and 15 minutes. What time did she finish her homework?

Flauer [41]

Answer:

6:00 or 6 o'clock

Step-by-step explanation:

1) Add 2 to the hours. So, 3+2=5

2) Add 15 minutes to 45 minutes. So, 15+45=60

3) 60 minutes is an hour, so therefore add one more hour. 5+1=6

4) There are 6 hours and 0 minutes.

So, the time that Renita finished her homework was 6:00.

Hope this helps!! ~Carley R.

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3 years ago

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Answer:

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