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3 years ago

Find the two-digit number satisfying the following two conditions.

2 answers:

7 0

Let x = the 10's digit
Let y - units digit
then
10x + y = original number
:
Write and equation for each statement:
;
"the units digits of a two-digit number is 3 more than twice the tens digit."
y = 2x + 3
:
"If the digits are reversed, the new number is 9 less than 4 times the original number."
10y + x = 4(10x+y) - 9
10y + x = 40x + 4y - 9
10y - 4y = 40x - x - 9
6y = 39x - 9
:

Find the original number.
:
Substitute (2x+3) for y in the above equation:
6(2x+3) = 39x - 9
12x + 18 = 39x - 9
18 + 9 = 39x - 12x
27 = 27x
x = 1
:
Then using y = 2x+3
y = 2(1) + 3
y = 5
:
Original number = 15
:
:
Check solution in the statement:
"If the digits are reversed, the new number is 9 less than 4 times the original number."
51 = 4(15) - 9

givi [52]3 years ago

7 0

The answer to the question is 72. This can be found either by trial and error, or by setting up a system of equations.

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Consider the right triangle. What is the length of the hypotenuse?

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The answer would be 53

Step-by-step explanation:

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4 years ago

Raj paid $31.86 for a new basketball. The price he paid included sales tax of 6.25%.

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3 years ago

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liq [111]

Answer:

the answer is A

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3 years ago

A survey is to be conducted in which a random sample of residents in a certain city will be asked whether they favor or oppose t

marshall27 [118]

Answer:

n=269 residents should be sample required to be sure that a 90% confidence interval for the proportion who favor the construction will have a margin of error no greater than 0.05

Step-by-step explanation:

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".

$p$ represent the real population proportion of interest

$\aht p$ represent the estimated proportion for the sample

n is the sample size required (variable of interest)

$z$ represent the critical value for the margin of error

The population proportion have the following distribution

$p \sim N(p,\sqrt{\frac{\hat p(1-\hat p)}{n}})$

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 90% of confidence, our significance level would be given by $\alpha=1-0.90=0.10$ and $\alpha/2 =0.05$ . And the critical value would be given by:

$z_{\alpha/2}=-1.64, z_{1-\alpha/2}=1.64$

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 assume that the estimates proportion is 0.5 since we don't have other info provided to assume a different value. And replacing into equation (b) the values from part a we got:

$n=\frac{0.5(1-0.5)}{(\frac{0.05}{1.64})^2}=268.96$

And rounded up we have that n=269

4 0

3 years ago