What is 68 3/4 of 16??

snow_tiger [21]

B) y=34.84x-2054 I believe that is the right answer

7 0

3 years ago

MathematicalUse Number Sense Duane and Mick are savingtheir money to build a tree house. Duane adds $5 to their piggybank every

Elina [12.6K]

Assuming they start saving at 0 dollars

45=total=duanesavings+micksavings
duanesavings=confusing, I will explain
mick savings =amount saves per week times number of weeks

duane saves 5 dollars every other week, aka 2.5 dollars per 1 week
DS=2.5w
MS=2w

since they save at same time and at that week, when the weeks are equal (w=w), 45 it total

DS+MS=45
2.5w+2w=45
4.5w=45
divide by 4.5 both sides
w=10

10 weeks

8 0

3 years ago

Can you help me please

Mekhanik [1.2K]

Answer:

-3

1.1 ×10

Explanation: when you divide it it comes to .0011

and with significant figures you move the decimal over until it is right after the first number that is not zero. so that would change .0011 to 1.1

also with significant figures if you move the decimal to the right you exponent by the 10 will be negative and if you move it to the left it will be positive. so I. this case we are moving g to the right 3 digits so our exponent will be negative 3.

and because the answer is still really. 0011 you multiply

-3

1.1 × 10

5 0

3 years ago

Nitrates are groundwater contaminants derived from fertilizer, septic tank seepage and other sewage. Nitrate poisoning is partic

o-na [289]

Answer:

a) $n=\frac{0.5(1-0.5)}{(\frac{0.02}{1.96})^2}=2401$

And rounded up we have that n=2401

b) $n=\frac{0.07(1-0.07)}{(\frac{0.02}{1.96})^2}=625.22$

And rounded up we have that n=626

And we see that if we have previous info about p the sample size varies a lot.

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 95% of confidence, our significance level would be given by $\alpha=1-0.95=0.05$ and $\alpha/2 =0.025$ . And the critical value would be given by:

$z_{\alpha/2}=-1.96, z_{1-\alpha/2}=1.96$

Part a

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 $ME =\pm 0.02$ 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)

Since we don't have prior information about the population proportion we can use ase estimator $\hat p =0.5$ . And replacing into equation (b) the values from part a we got:

$n=\frac{0.5(1-0.5)}{(\frac{0.02}{1.96})^2}=2401$

And rounded up we have that n=2401

Part b

For thi case the estimator for p is $\hat p =0.07$

$n=\frac{0.07(1-0.07)}{(\frac{0.02}{1.96})^2}=625.22$

And rounded up we have that n=626

And we see that if we have previous info about p the sample size varies a lot.

4 0

3 years ago

The equation x^3+x^2+ax-4=0 has one root equal to -2. Find the value of a.

Vedmedyk [2.9K]

Answer:

a = - 4

Step-by-step explanation:

Given x = - 2 is a root then f(- 2) = 0

f(x) = x³ + x² + ax - 4, thus

f(- 2) = (- 2)³ + (- 2)² - 2a - 4 = 0, that is

f(- 2) = - 8 + 4 - 2a - 4 = 0, thus

- 8 - 2a = 0 ( add 8 to both sides )

- 2a = 8 ( divide both sides by - 2 )

a = - 4

5 0

3 years ago