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2 years ago

What is the square root of 21

Mathematics

1 answer:

Andru [333]2 years ago

4 0

Answer:

4.58

Step-by-step explanation:

21 is not a perfect square, but lies between the perfect squares 16 and 25. Thus, √21 lies between √16 and √25, that is, between 4 and 5. Since 21 is closer to 25 than to 16, √21 is closer to 5 than to 4. A rough estimate of √21 would be 4.7.

√21 done on a calculator comes out to 4.58.

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A manager is comparing wait times for customers in a coffee shop based on which employee is

anyanavicka [17]

Using the t-distribution, as we have the standard deviation for the sample, it is found that there is a significant difference between the wait times for the two populations.

<h3>What are the hypothesis tested?</h3>

At the null hypothesis, we test if there is no difference, that is:

$H_0: \mu_A - \mu_B = 0$

At the alternative hypothesis, it is tested if there is difference, that is:

$H_1: \mu_A - \mu_B = 0$

<h3>What are the mean and the standard error of the distribution of differences?</h3>

For each sample, we have that:

$\mu_A = 73, s_A = \frac{2}{\sqrt{100}} = 0.2$

$\mu_B = 74, s_B = \frac{4}{\sqrt{100}} = 0.4$

For the distribution of differences, we have that:

$\overline{x} = \mu_A - \mu_B = 73 - 74 = -1$

$s = \sqrt{s_A^2 + s_B^2} = \sqrt{0.2^2 + 0.4^2} = 0.447$

<h3>What is the test statistic?</h3>

It is given by:

$t = \frac{\overline{x} - \mu}{s}$

In which $\mu = 0$ is the value tested at the null hypothesis.

Hence:

$t = \frac{\overline{x} - \mu}{s}$

$t = \frac{-1 - 0}{0.447}$

$t = -2.24$

<h3>What is the p-value and the decision?</h3>

Considering a one-tailed test, as stated in the exercise, with 100 - 1 = 99 df, using a t-distribution calculator, the p-value is of 0.014.

Since the p-value is less than the significance level of 0.05, it is found that there is a significant difference between the wait times for the two populations.

More can be learned about the t-distribution at brainly.com/question/16313918

8 0

2 years ago

The radius of the base of a cylinder is increasing at a rate of 7 millimeters per hour. The height of the cylinder is fixed at 1

Ilya [14]

Answer:

The rate of change of the volume of the cylinder at that instant = $791.28\ mm^3/hr$

Step-by-step explanation:

Given:

Rate of increase of base of radius of base of cylinder = 7 mm/hr

Height of cylinder = 1.5 mm

Radius at a certain instant = 12 mm

To find rate of change of volume of cylinder at that instant.

Solution:

Let $r$ represent radius of base of cylinder at any instant.

Rate of increase of base of radius of base of cylinder can be given as:

$\frac{dr}{dt}=7\ mm/hr$

Volume of cylinder is given by:

$V=\pi\ r^2h$

Finding derivative of the Volume with respect to time.

$\frac{dV}{dt}=\pi\ h\ 2r\frac{dr}{dt}$

Plugging in the values given:

$\frac{dV}{dt}=\pi\ (1.5)\ 2(12)(7)$

$\frac{dV}{dt}=252\pi$

Using $\pi=3.14$

$\frac{dV}{dt}=252(3.14)$

$\frac{dV}{dt}=791.28\ mm^3/hr$ (Answer)

Thus rate of change of the volume of the cylinder at that instant = $791.28\ mm^3/hr$

6 0

2 years ago

a rectangle is 4 times as long as it wide. if the length is increased by 4 inches and the width is decreased by 1 inch, the area

Mekhanik [1.2K]

$x-\ width\\
y-\ length\\
4x=y\\
(y+4)(x-1)=60\\
(4x+4)(x-1)=60\\
4x^2-4x+4x+4=60\ \ | subtract\ 4\\
4x^2=56\ \ | divide\ by\ 4\\
x^2=14\\
x=\sqrt{14}\\
y=4\sqrt{14}\\\\
Dimensions:\ width=\sqrt{14}in,\ length=4\sqrt{14}in.$

6 0

3 years ago

In 1982 Abby’s mother scored at the 93rd percentile in the math SAT exam. In 1982 the mean score was 503 and the variance of the

oksian1 [2.3K]

Answer:

The percentle for Abby's score was the 89.62nd percentile.

Step-by-step explanation:

Problems of normally distributed samples are solved using the z-score formula.

In a set with mean $\mu$ and standard deviation(which is the square root of the variance) $\sigma$ , the zscore of a measure X is given by:

$Z = \frac{X - \mu}{\sigma}$

The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the pvalue, we get the probability that the value of the measure is greater than X.

Abby's mom score:

93rd percentile in the math SAT exam. In 1982 the mean score was 503 and the variance of the scores was 9604.

93rd percentile. X when Z has a pvalue of 0.93. So X when Z = 1.476.

$\mu = 503, \sigma = \sqrt{9604} = 98$