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3 years ago

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The ratio of the number of A's in the class to B's in the class was 2:5. How many people got A's if there were 40 people who got

B's?

2 answers:

Umnica [9.8K]3 years ago

7 0

Answer:

16 students got an A

Step-by-step explanation:

Set up an equation to compare the ratio to the scores:

$\frac{2}{5} = \frac{x}{40}$

Cross multiply:

80 = 5x

Divide each side by 5:

x = 16

Now, check if $\frac{16}{40} = \frac{2}{5}$

16/8 = 2

40/8 = 5

The ratios are the same! Therefore, 16 students got an A!

Hope this helps! Feel free to contact me if you have any questions :)

oksano4ka [1.4K]3 years ago

3 0

$Total- no- of- students = 56\\A -students = Total- no- of- students - B-students\\A - students = 56 - 40\\A students = 16$ Answer:

A Students = 16 students

Step-by-step explanation:

$A :B\\2 :5\\ No- of -A -students =?\\No- of -B -students = 40\\2+5 =7\\\frac{5}{7} *x = 40\\\frac{5x}{7} =40\\Cross - multiply\\280 = 5x\\Divide-both-sides-of-the-equation -by 5\\\\\frac{280}{5} = \frac{5x}{5} \\x = 56$

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2 years ago

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Step-by-step explanation:

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3 years ago

Read 2 more answers

You want to rent an unfurnished one-bedroom apartment in Boston next year. The mean monthly rent for a random sample of 10 apart

Brilliant_brown [7]

Answer:

90% confidence interval: (2186.53;2881.47)

95% confidence interval: (2118.73;2949.27)

99% confidence interval: (1987.37;3080.63)

For the last part is not the best way say : "This interval describes the price of 95% of the rents of all the unfurnished one-bedroom apartments in the Boston area."

The best interpretation is this one: "We are 95% confident that the actual mean for the rents of unfurnished one-bedroom apartments in the Boston area is between (2118.73;2949.27)"

Step-by-step explanation:

1) 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".

$\bar X=2534$ represent the sample mean

$\mu$ population mean (variable of interest)

$\sigma=670$ represent the population standard deviation

n=10 represent the sample size

90% confidence interval

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 0.90 or 90%, the value of $\alpha=0.1$ and $\alpha/2 =0.05$ , and we can use excel, a calculator or a tabel to find the critical value. The excel command would be: "=-NORM.INV(0.05,0,1)".And we see that $z_{\alpha/2}=1.64$

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

$2534-1.64\frac{670}{\sqrt{10}}=2186.53$

$2534+1.64\frac{670}{\sqrt{10}}=2881.47$

So on this case the 90% confidence interval would be given by (2186.53;2881.47)

95% confidence interval

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 0.95 or 95%, the value of $\alpha=0.05$ and $\alpha/2 =0.025$ , and we can use excel, a calculator or a tabel to find the critical value. The excel command would be: "=-NORM.INV(0.025,0,1)".And we see that $z_{\alpha/2}=1.96$

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

$2534-1.96\frac{670}{\sqrt{10}}=2118.73$

$2534+1.96\frac{670}{\sqrt{10}}=2949.27$

So on this case the 95% confidence interval would be given by (2118.73;2949.27)

99% confidence interval

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 tabel to find the critical value. The excel command would be: "=-NORM.INV(0.005,0,1)".And we see that $z_{\alpha/2}=2.58$

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

$2534-2.58\frac{670}{\sqrt{10}}=1987.37$

$2534+2.58\frac{670}{\sqrt{10}}=3080.63$

So on this case the 99% confidence interval would be given by (1987.37;3080.63)

For the last part is not the best way say : "This interval describes the price of 95% of the rents of all the unfurnished one-bedroom apartments in the Boston area."

The best interpretation is this one: "We are 95% confident that the actual mean for the rents of unfurnished one-bedroom apartments in the Boston area is between (2118.73;2949.27)"

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3 years ago

Factorize the equation <br>2b2 - 33b + 16 = 0

Tamiku [17]

Answer:

(2b-1) (b-16)

Step-by-step explanation:

(2b^2-32b)(-b+16)

2b(b-16) -1(b-16)

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3 years ago