what is this??
i need help

What Is This??i Need Help

Answers

Answer 1

Answer:

uhmm sry i dont understand too

Related Questions

A random sample of 100 chemistry students were asked how many lab classes he or she was enrolled in september 2000. the results showed a mean of 1.65 lab classes with a standard deviation of 1.39. ten years later, a similar survey was conducted to determine if the distribution changed. the 2010 sample mean was 1.82 with a standard deviation of 1.51. do the data provide statistical evidence that the mean number of lab classes taken in the first survey is different from the survey taken 10 years later? perform the appropriate test using a = 0.02​

Answers

Using the t-distribution, as we have the standard deviation for the samples, it is found that the data does not provide statistical evidence that there is a difference.

What are the hypotheses tested?

At the null hypotheses, it is tested if there is no difference in the means, that is, the subtraction is of 0, hence:

[tex]H_0: \mu_1 - \mu_2 = 0[/tex]

At the alternative hypotheses, it is tested if there is a difference, hence:

[tex]H_1: \mu_1 - \mu_2 \neq 0[/tex]

What are the mean and the standard error of the distribution of differences?

For each sample, they are given by:

[tex]\mu_1 = 1.82, s_1 = \frac{1.51}{\sqrt{100}} = 0.151[/tex]

[tex]\mu_2 = 1.65, s_2 = \frac{1.39}{\sqrt{100}} = 0.139[/tex]

Hence, for the distribution of differences, they are given by:

[tex]\overline{x} = \mu_1 - \mu_2 = 1.82 - 1.65 = 0.17[/tex]

[tex]s = \sqrt{s_1^2 + s_2^2} = \sqrt{0.151^2 + 0.139^2} = 0.205[/tex]

What is the test statistic?

The test statistic is given by:

[tex]t = \frac{\overline{x} - \mu}{s}[/tex]

In which [tex]\mu = 0[/tex] is the value tested at the null hypothesis.

Then:

[tex]t = \frac{\overline{x} - \mu}{s}[/tex]

[tex]t = \frac{0.17 - 0}{0.205}[/tex]

[tex]t = 0.83[/tex]

What is the decision?

Considering that it is a two-tailed test, as we are testing if the mean is different of a value, with 100 + 100 - 2 = 198 df and a significance level of 0.02, the critical value is of [tex]|t^{\ast}| = 2.3453[/tex].

Since the absolute value of the test statistic is less than the critical value, we do not reject the null hypothesis, which means that the data does not provide statistical evidence that there is a difference.

More can be learned about the t-distribution at https://brainly.com/question/13873630

Can y’all please solve this

Answers

A). The answer is x = -4
Work:
3 - x = 11 + x
3 - x - 3 = 11 + x - 3
-x = x + 8
-x - x = x + 8 - x
-2x = 8
-2x/-2 = 8/-2
Answer: x = -4

B). The answer is x = 6
Work:
2x + 7 = 3x + 1
2x + 7 = 3x + 1 - 7
2x = 3x - 6
2x - 3x = 3x - 6 - 3x
-x = -6
-x/-1 = -6/-1
Answer x = 6

C). Answer: x = 4/3
Work:
8 - 2x = 4 + x
8 - 2x - 8 = 4 + x - 8
-2x = x - 4
-2x - x = x - 4 - x
-3x = -4
-3x/-3 = -4/-3
Answer: x = 4/3

D). Answer: x = 2
Work:
4x + 2 = 2x + 6
4x + 2 - 2 = 2x + 6 - 2
4x = 2x + 4
4x - 2x = 2x + 4 - 2x
2x = 4
2x/2 = 4/2
Answer: x = 2

A circle is to be drawn with radius 3.5 inches. the radius is measured as 3.6 instead, what error does this cause in the area of the circle?(leave your answer in terms of pi )

Answers

Answer:

[tex]0.71\pi\: in^2[/tex]

Step-by-step explanation:

[tex]r_1= 3.5\: in[/tex]

[tex]r_2= 3.6\: in[/tex]

[tex]A_1=\pi r_1^2=\pi(3.5)^2= 12.25\pi \:in^2[/tex]

[tex]A_2=\pi r_2^2=\pi(3.6)^2= 12.96\pi \:in^2[/tex]

[tex]Difference\: in \:area =A_2-A_1=0.71\pi\:in^2[/tex]

[tex]\implies Error \:in\: the \:area \:of\: the \:circle = 0.71\pi\: in^2[/tex]

The volume of a cone is 400π cm3. The height of the cone is 12 cm.

What is the length of the radius of the cone?

Answers

Answer:

10 cm

Step-by-step explanation:

The volume of cone formula:

V = 1/3πr²h

Substitute te given values into the formula and solve for r:

400π = 1/3πr²(12)100 = r²r = √100r = 10

Answer:

10 cm

Step-by-step explanation:

Volume of a cone

  [tex]\sf V= \dfrac{1}{3} \pi r^2 h[/tex]

where:

V = volumer = radiush = height

Given information:

V = 400π cm³h = 12 cm

To find the length of the radius, substitute the given values into the formula and solve for r:

[tex]\begin{aligned}\sf V& = \sf \dfrac{1}{3} \pi r^2 h\\\\\implies \sf 400 \pi & = \sf \dfrac{1}{3} \pi r^2(12)\\\\ \sf 400 \pi & = \sf \dfrac{12}{3} \pi r^2\\\\ \sf 400 \pi & = \sf 4\pi r^2\\\\ \sf \dfrac{400 \pi}{4 \pi} & = \sf r^2\\\\ \sf r^2 & = \sf 100 \\\\ \sf \sqrt{r^2} & = \sf \sqrt{100}\\\\ \sf r & = \sf 10\end{aligned}[/tex]

Therefore, the length of the radius of the cone is 10 cm.

Learn more about cones here:

https://brainly.com/question/27845349

https://brainly.com/question/27825174

Please help me with complement or supplement of an angles.

Answers

Answer: 101 degrees

Step-by-step explanation:

Please help I will give brainliest.

Answers

    To answer these questions, we need to graph the equation as well as turn this into slope-intercept form, this is y = mx + b. The m is our slope and the b is the y-intercept.

-> See attached for graph

   1.5x + 4.5y = 18

   4.5y = -1.5x + 18

   y = -[tex]\frac{1}{3}[/tex]x + 4

      The slope is -[tex]\frac{1}{3}[/tex]

                y = -1/3x + 4

       The y-intercept is (0, 4)

                The x-intercept is (12, 0)

If x = 2and y = - 2 , find the value of 4x ^ 2 * y ^ - 2​

Answers

hello!

=========================================================

Plug in the values of the variables & simplify:-

[tex]\longrightarrow\pmb{4x^2y^2}[/tex]

The values of the variables are:-

[tex]\bigstar{\boxed{x=2~and~y=-2}[/tex]

Simplify:-

[tex]\longrightarrow\pmb{4(2)^2(-2)^2}[/tex]

[tex]\longrightarrow\pmb{4*4-4}[/tex]

[tex]\longrightarrow\pmb{16-4}[/tex]

[tex]\longrightarrow\pmb{12}[/tex]

==========================================================

note:-

Hope everything is clear; if you need any clarification/explanation, kindly let me know, and I'll comment and/or edit my answer :)

Answer:

the answer for this is 4.

Question 1
1 pts
Use the GSS file to investigate whether or not Americans use the Internet at least 7
hours per week (estimating an hour per day). Perform the One Sample T Test
procedure (as presented in SPSS Demonstration 1) to do this test with the variable
WWWHR. Do the test at the .01 significance level. What is the T [1]?
Put 40 in the

Answers

The computation of the significance level shows that the p-value is less than 0.01 and the conclusion is that Americans use the internet more than 7 hours weekly.

What is a significance level?

It should be noted that the significance level simply means the probability that an event occured by chance.

From the complete question, it can be noted that at 0.01 significance level, the t statistic is 17.873 and the degree of freedom is 539.

The p-value for the right tailed test is 0. Therefore, since the p value is less than 0.01, we will reject the null hypothesis. The conclusion is that Americans use the internet more than 7 hours weekly.

Learn more about significance level on:

https://brainly.com/question/9163177

A cylinder has a height of 9 millimeters and a radius of 11 millimeters. What is its volume? Use ​ ≈ 3.14 and round your answer to the nearest hundredth.

Answers

Answer:

3419.46 mm3

Step-by-step explanation:

volume of cylinder = area of circle x heoight

A of circle  = pie r sqy = 3.14 x 11 x 11 = 379.94

379.94 x 9 = 3419.46

Unit 10: circles homework 6: arc & angle measures

**please explain how you get your answer**

Answers

Circles are perfectly round figures that have only one central angle

The measure of JML is 233 degrees

How to determine the measures of angle JML?

The question is incomplete, so I will give a general explanation using the following parameter:

JL = 127 degrees.

Angles at a point add up to 360 degrees

So, we have:

JML + 127 = 360

Make JML the subject

JML = 360 - 127

JML = 233

Hence, the measure of JML is 233 degrees

Read more about circles and arcs at:

brainly.com/question/25305793

Please I need answer quickly

how many ways can you form 3 groups from 18 people so that there's 3 people in first group, 6 people in the second group and 9 people in third

Answers

Answer:

4 084 080 ways

Step-by-step explanation:

The number of ways is :

[tex]C^{3}_{18}\times C^{6}_{15}\times C^{9}_{9}[/tex]

___________

Since

  18C3=816

  15C6=5 005

  9C9=1

then

[tex]C^{3}_{18}\times C^{6}_{15}\times C^{9}_{9}=816\times5005\times1= 4\ 084\ 080[/tex]

HELP ASAP ILL MARK BRAINLIST

1.State whether ∆RST is similar to ∆UVW and why. Show your work and explain what postulate or theorem you used to solve.

Answers

Answer:

Yes they are similar

Step-by-step explanation:

Divide the length VW by ST

24 ÷ 16 = 1.333

Divide the length VU by SR

16 ÷ 12 = 1.333

→ As they have the same scale factor, they are similar.

Answer:

Step-by-step explanation:

First when triangles are similar angles are congruent and the side ratio are the same .

18/24=12/16=m/32

3/4=3/4=m/32

3/4=m/32

4m=96

m=24

help me please!!!!!!!!!

Answers

Answer:

A = 5

I hope you have an amazing day!

The person that answered before me is correct!
A=5
(I just stole their answer so give them full credit heh)

Pls answer
5= -5 (6n + 8)

Answers

Answer:

the value of n is -1.5

Step-by-step explanation:

I hope the question was to find the unknown.

Answer:

n= -3/2

Step-by-step explanation:

Isolate the variable by dividing each side by factors that don't contain the variable.

Exact Form:

n=−32

Decimal Form:

n=-1.5

Mixed Number Form:

n=−112

∠A and ∠B are supplementary. The measure of ∠A is 34°.

What is the measure of ∠B?

Enter your answer in the box.


Please help!

Answers

Answer:

146

Step-by-step explanation:

Given;

 ∠A and ∠B are supplementary. The measure of ∠A is 34°.

To Find;

What is the measure of ∠B?

Note:

Supplementary = 180 degree

Solve:

Since supplementary = 180 degree

34 + x = 180

Subtract 34 from both sides

x + 34 - 23 = 180 - 34

Simplify

x = 146

Hence, the measure of ∠B is 146

~Learn with Lenvy~

Find the 7th term of the geometric sequence whose common ratio is 2/3 and whose first term is 6.

Answers

Hope it helpssss…….hehe

A median drawn to a side of a triangle is
Select one:
O a. a ray
O b. a segment
O c. a line

Answers

Ima say B a segment

6
It costs 35p per minute to hire a powerful computer. How much will it cost to hire the
computer from 07:40 to 08:15?

Answers

Answer:

1225p

Step-by-step explanation:

1 minute = 35p

07:40 to 08:15 : 35 minute

=> 35 minute *35p=1225p

Write the following expression using an exponent.
1x7x7x7x7x7

Answers

Answer:

7^5

Step-by-step explanation:

Hopefully this helps :)

Evaluate each finite series for the specified number of terms. 1+2+4+...;n=5

Please show work

Answers

Answer:

31

Step-by-step explanation:

The series are given as geometric series because these terms have common ratio and not common difference.

Our common ratio is 2 because:

1*2 = 2

2*2 = 4

The summation formula for geometric series (r ≠ 1) is:

[tex]\displaystyle \large{S_n=\frac{a_1(r^n-1)}{r-1}}[/tex] or [tex]\displaystyle \large{S_n=\frac{a_1(1-r^n)}{1-r}}[/tex]

You may use either one of these formulas but I’ll use the first formula.

We are also given that n = 5, meaning we are adding up 5 terms in the series, substitute n = 5 in along with r = 2 and first term = 1.

[tex]\displaystyle \large{S_5=\frac{1(2^5-1)}{2-1}}\\\displaystyle \large{S_5=\frac{2^5-1}{1}}\\\displaystyle \large{S_5=2^5-1}\\\displaystyle \large{S_5=32-1}\\\displaystyle \large{S_5=31}[/tex]

Therefore, the solution is 31.

__________________________________________________________

Summary

If the sequence has common ratio then the sequence or series is classified as geometric sequence/series.

Common Ratio can be found by either multiplying terms with common ratio to get the exact next sequence which can be expressed as [tex]\displaystyle \large{a_{n-1} \cdot r = a_n}[/tex] meaning “previous term times ratio = next term” or you can also get the next term to divide with previous term which can be expressed as:

[tex]\displaystyle \large{r=\frac{a_{n+1}}{a_n}}[/tex]

Once knowing which sequence or series is it, apply an appropriate formula for the series. For geometric series, apply the following three formulas:

[tex]\displaystyle \large{S_n=\frac{a_1(r^n-1)}{r-1}}\\\displaystyle \large{S_n=\frac{a_1(1-r^n)}{1-r}}[/tex]

Above should be applied for series that have common ratio not equal to 1.

[tex]\displaystyle \large{S_n=a_1 \cdot n}[/tex]

Above should be applied for series that have common ratio exactly equal to 1.

__________________________________________________________

Topics

Sequence & Series — Geometric Series

__________________________________________________________

Others

Let me know if you have any doubts about my answer, explanation or this question through comment!

__________________________________________________________

What ratio forms a proportion with 2/3?
A. 2/4 B. 3/4 C. 4/6 D. 3/2

Answers

Answer:

c

Step-by-step explanation:

because you can simplify 4/6 by 2.

2 goes into 4 twice and then 2 goes into 6 3 times

2/3

The length of one leg of an isosceles right triangle is 3 ft. What is the perimeter of the triangle? 3 3 StartRoot 2 EndRoot ft 3 3 StartRoot 3 EndRoot ft 6 3 StartRoot 2 EndRoot ft 6 3 StartRoot 3 EndRoot ft.

Answers

The perimeter of the isosceles right triangle comes to be 6+3√2.

Given that the length of one leg of an isosceles right triangle = 3 ft

What is an isosceles right triangle?

A right-angle triangle having sides other than hypotenuse equal to each other is called an isosceles right triangle.

So, The length of the other leg of an isosceles right triangle = 3 ft

From Pythagoras theorem

Hypotenuse²=Perpendicular²+Base²

So, in the given isosceles right triangle

Hypotenuse²=Leg 1²+Leg2²

Leg 1=Leg2 = 3 feet

Hypotenuse² =  3²+3²

Hypotenuse = 3√2 ft.

So, the perimeter of the triangle = 3+3+ 3√2

The perimeter of the triangle =6+3√2

Therefore, The perimeter of the isosceles right triangle comes to be 6+3√2.

To get more about the right triangle visit:

https://brainly.com/question/22364396

Answer:

6 + 3 StartRoot 2 EndRoot ft

Step-by-step explanation:

Edge2022

328 rattle snakes in 2008. How many will there be in 2024?
402853
21498508
32800
20992

Answers

Answer:

[tex]{ \tt{12 \: months = 328}} \\ { \tt{(12 \times 15) = \frac{(15 \times 328)}{1} }} \\ \\ = { \tt{4920}}[/tex]

Answer:

2008=328

2024=?

Step-by-step explanation:

12×13 = 16×328/1

answer is it 1 2 3 or 4

Answers

Answer: C. 125.66 in²

Step-by-step explanation:

      This is asking us to find the surface area of this cone. We can use the formula and solve.

A = πrl + πr²

A = π(4)(6) + π(4)²

A = π(4)(6) + π(4)²

A ≈ 125.66 in²

      It would take C. 125.66 in² of toilet paper to cover the surface of this cone.

Convert 30% to a fraction in lowest terms

Answers

Answer:

3/10

Step-by-step explanation:

Hope this helped

Drag each tile to the correct box.

The given steps for constructing a line tangent to circle O that is tangent to the circle at point P on the circle are listed out of order. Arrange the steps in the correct sequence.


A. Without changing the compass width, place the compass on R and make another arc, intersecting the first, and label the intersection S.


B. Draw a line through P and S.


C. With the compass on P, draw an arc on each side of P. Label the intersections Q and R.


D. Draw a straight line from the center, O, through P and extending past P.


E. With the compass on Q, set its width to a setting greater than. Make an arc outside the circle

Answers

Answer:

D, C, E, A, B

Step-by-step explanation:

This is essentially the construction of a perpendicular bisector.

D. Draw a straight line from the center, O, through P and extending past P

C. With the compass on P, draw an arc on each side of P. Label the intersections Q and R.

E. With the compass on Q, set its width to a setting greater than. Make an arc outside the circle

A. Without changing the compass width, place the compass on R and make another arc, intersecting the first, and label the intersection S

B. Draw a line through P and S.

How to find arc in math?

Arc length is the distance between 2 points in the arc of a circle. The arc of the circle could be calculated by using the following formula: Arc: Length = Θ x r

What does arc mean?

In general, the arc is a portion of the curve. In mathematics, unless otherwise begain, then arc usually refers to the portion of the circle. Types of arcs. A chord, or the central angle and an inscribed angle may divide the circle into 2 arcs.

Learn more about arc here https://brainly.com/question/27673190

#SPJ2

Help please I need helps please

Answers

Answer:

I belive the answer is 96 ft.

Step-by-step explanation:

Hope that helps!

Write f(x) = 2x2 – 44x 185 in vertex form. To write f(x) = 2x2 – 44x 185, factor out from the first two terms. Next, form a perfect square trinomial keeping the value of the function equivalent: f(x) = 2(x2 – 22x 121) 185 – 242 The function written in vertex form is f(x) = (x – )2.

Answers

The quadratic function f(x) = 2x² – 44x + 185 is written in vertex form is f(x) = 2(x –  11)² – 57.

What is a quadratic equation?

It is a polynomial that is equal to zero. Polynomial of variable power 2, 1, and 0 terms are there. Any equation having one term in which the power of the variable is a maximum of 2 then it is called a quadratic equation.

The quadrattic equation is f(x) = 2x² – 44x + 185.

Take common 2 from the equation, we have

[tex]f(x) = 2(x^2 - 22x )+ 185[/tex]

Add and subtract 121, we have

[tex]f(x) = 2(x^2 - 22x +121 - 121 )+ 185\\\\f(x) = 2[(x^2 - 11)^2-121]+ 185\\\\f(x) = 2(x-11)^2 - 242 + 185\\\\f (x ) = 2(x-11)^2 -57[/tex]

And we know that the standard equation

f(x) = a(x - h)² + k

On comparing, we have

The vertex (h, k) is (11, -57).

More about the quadratic equation link is given below.

https://brainly.com/question/2263981

Answer:

1. 2

2. 2

3. 11

4. -57

Step-by-step explanation: actual answers

2. What is the measure of angley?
(2 pts.)
52°
to

Answers

Answer: the answer is 55 degrees

Step-by-step explanation:

Find the sum of the following polynomials
(3x^3+ 8x^2– 3) + (7x^3- 4x + 4)

Answers

Answer:

10x^3+8x^2-4x+1 is answer

i also agree with them^^ mark them the brainliest
Other Questions
A frequency generator sends a 550 Hz sound wave through both water and ice. A 3 column by 4 row table. Column 1 is titled Medium and includes the following entries: Ice, Water, Steam. Column 2 is titled Temperature (degrees Celsius) and includes the following entries: 0, 25, 100. Column 3 is titled Speed of Sound (meters per second) and includes the following entries: 3200 meters per second, 1500 meters per second, 346 meters per second. What is the difference in wavelength between the wave produced in ice and the wave produced in water? 2. 1 m 3. 1 m 5. 2 m 8. 5 m. 8. Rita looks at the floor plan of a room that was drawn with scale factor 1 inch equals 4 feet. She multiplied the perimeter of the drawing by four and ordered that many feet of molding. She multiplied the area of the drawing by four and ordered that many square feet of carpeting. When the orders arrived, Rita had enough molding, but the carpet covered only of the room. Explain the error. Approximately how many grams of radium will remain after 4 grams have decayed for 2400 years A decrease in the activity of the antidiuretic hormone produced by the posterior lobe of the pituitary gland results in Select the correct text in the passage.Which sentence in this excerpt from Ernest Hemingway's "In Another Country" uses parallelism?In the fall the war was always there, but we did not go to it any more. It was cold in the fall in Milan and the dark came very early. Then theelectric lights came on, and was pleasant along the streets looking in the windows. There was much game hanging outside the shops, and thesnow powdered in the fur of the foxes and the wind blew their talls. The deer hung stiff and heavy and empty, and small birds blew in the windand the wind turned their feathers. It was , cold fall and the wind came down from the mountains. Consult 3 sources on how corruption becomes way of life Amira decides to estimate the volume of an apple by modeling it as a sphere. She measures its circumference as 43.4 cm. Find the apples's volume in cubic centimeters. Round your answer to the nearest tenth if necessary. Ciara, an ornithologist, has 444 bird feeders at separate locations. She wonders if birds are equally likely to visit each of the feeders. She recorded data for a sample of 350350350 recent visits. Here are the results: Feeder \#1#1\#, 1 \#2#2\#, 2 \#3#3\#, 3 \#4#4\#, 4 Observed visits 808080 909090 929292 888888 Ciara wants to perform a \chi^2 2 \chi, squared goodness-of-fit test to determine if these results suggest that birds visit one specific feeder more often than the other feeders. What is the expected count of visits to the third feeder? You may round your answer to the nearest hundredth. 10 high school seniors were asked how many hours they work in a typical week during summer the data is shown below. STEP BY STEP ANSWERS ONLY What type of epithelial tissue is found in the proximal and distal convoluted tubules I Need help again :) A teacher used the change of base formula to determine whether the equation below is correct. (log Subscript 2 Baseline 10) (log Subscript 4 Baseline 8) (log Subscript 10 Baseline 4) = 3 Which statement explains whether the equation is correct? The equation is correct since (log Subscript 2 Baseline 10) (log Subscript 4 Baseline 8) (log Subscript 10 Baseline 4) = log (2 times 10) times log (4 times 8) times log (10 times 4). = log (20) times log (32) times log (40). =3 The equation is correct since (log Subscript 2 Baseline 10) (log Subscript 4 Baseline 8) (log Subscript 10 Baseline 4) = StartFraction log 10 Over log 2 EndFraction times StartFraction log 8 Over log 4 EndFraction times StartFraction log 4 Over log 10 EndFraction. = StartFraction log 8 Over log 2 EndFraction. = 3 The equation is correct since (log Subscript 2 Baseline 10) (log Subscript 4 Baseline 8) (log Subscript 10 Baseline 4) = StartFraction log 10 Over log 2 EndFraction times StartFraction log 8 Over log 4 EndFraction times StartFraction log 4 Over log 10 EndFraction. = StartFraction log 8 Over log 2 EndFraction. = 4. The equation is not correct since (log Subscript 2 Baseline 10) (log Subscript 4 Baseline 8) (log Subscript 10 Baseline 4) = log StartFraction 10 Over 2 EndFraction times log eight-fourths times log four-tenths. = log 5 times log 2 times log 0. 4. = negative 0. 8. 7 oraciones con conectores de tiempo y los clasifican porfavor Describe how an ecosystem that contains insects, water, algae, and bird work together to provide life. u^2=64 solve using square root property Select the correct answer. which word best completes this sentence? oliver had a(n) ______ ability as a wide receiver, naturally dodging tackles and making his way down the football field. a. cordial b. inherent c. avengeful d. dispersible e. compliant Explain the structure and function of the eye as a sensory receptor including the role of;A)The cornea and lens B)The irisC)Rod and cone cells in the retinaNOTE - the letters listed are NOT answers, they are separate points that need clarifying. Calculate the determinant of this matrix:What is the first step?Step 1: Augment the matrix by copying columns 1 and 2 to the right of the matrixStep 2: Find the products along the main diagonals d1= 4 d2= 0 d3= 3Step 3: Find the products of the minor diagonalse1= 0e2= 16 e3= 2Step 4; Perform the final calculationd1+d2+d3-e1-e2-e3= -11(Got them all right on edge 2022) lord of the flies Chpt9: What seems to be the main conflict/s? how many solutions does 8B + 7v - 5 equals -11 + 15b