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3 years ago

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When 2 times a number is subtracted from 7 times the number, the result is 55. what is the number?

1 answer:

steposvetlana [31]3 years ago

8 0

Let n represent the number. You require
7n - 2n = 55
5n = 55 . . . . . . collect terms
n = 11 . . . . . . . divide by 5

The number is 11.

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The multiplicative inverse of -7/8 is

suter [353]

7/8 is a answer of this question

3 0

3 years ago

The Information Technology Department at a large university wishes to estimate the proportion of students living in the dormitor

nadya68 [22]

Answer:

$n=\frac{0.5(1-0.5)}{(\frac{0.05}{1.96})^2}=384.16$

And rounded up we have that n=385

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".

Solution to the problem

In order to find the critical value we need to take in count that we are finding the interval for a proportion, so on this case we need to use the z distribution. Since our interval is at 99% of confidence, our significance level would be given by $\alpha=1-0.99=0.01$ and $\alpha/2 =0.005$ . And the critical value would be given by:

$z_{\alpha/2}=-2.58, z_{1-\alpha/2}=2.58$

The margin of error for the proportion interval is given by this formula:

$ME=z_{\alpha/2}\sqrt{\frac{\hat p (1-\hat p)}{n}}$ (a)

And on this case we have that $ME =\pm 0.05$ and we are interested in order to find the value of n, if we solve n from equation (a) we got:

$n=\frac{\hat p (1-\hat p)}{(\frac{ME}{z})^2}$ (b)

We can use as an estimator for p $\hat p =0.5$ . And replacing into equation (b) the values from part a we got:

$n=\frac{0.5(1-0.5)}{(\frac{0.05}{1.96})^2}=384.16$

And rounded up we have that n=385

3 0

3 years ago

If the first differences of a sequence are a constant -7 and the third term is 22, find the first 5 terms of the sequence.

Andru [333]

Answer:

36, 29, 22, 15, 8

Step-by-step explanation:

Step 1: State known information

First difference is -7

Third term of the sequence is 22

Step 2: Find first 5 terms

You just need to add and subtract 7 to 22 and the answer 5 times

1. 36 +7

2. 29 +7

3. 22 <- We know 22 is the 3rd term

4. 15 -7

5. 8 -7

Therefore the first 5 terms of the sequence is 36, 29, 22, 15, 8

8 0

3 years ago

The sale price of an item is $180 after a 25% discount is applied. What is the original price of the item?

torisob [31]

original price is $240

5 0

3 years ago

Read 2 more answers

Consider the function: f(x) = 2x^2 - 1.5x - 5 and its graph.

Dominik [7]

Answer:

f(x) = -4x² + 19x - 18

Step-by-step explanation:

$f(x) = 2x^2 - 1.5x - 5$

i) If it is translated 2 units in the positive x direction, therefore we use f(x-2)

$y=f(x-2) = 2(x-2)^2 - 1.5(x-2) - 5\\y = 2(x^2-4x+4) - 1.5x+3 - 5\\y=2x^2-8x+8-1.5x+3-5\\y=2x^2-9.5x+6$

f(x) = 2x² - 9.5x + 6

If it is then translated 3 units in the positive y, we add 3 to the input function to get:

$y=f(x)+3=2x^2-9.5x+6+3\\y = 2x^2-9.5x+9$

ii) stretched vertically by a factor of 2, we multiply the function by 2 to get:

$y =2( 2x^2-9.5x+9) = 4x^2-19x+18\\y= 4x^2-19x+18$

iii) reflected across the x-axis

we multiply the parent function by –1, to get a reflection about the x-axis.

$y= -1(4x^2-19x+18)=-4x^2+19x-18\\y=f(x)=-4x^2+19x-18$

5 0

3 years ago