HELP :Write the expression as the
sine or cosine of an angle.

HELP :Write The Expression As Thesine Or Cosine Of An Angle.

Answers

Answer 1

Answer:

sin(4π/21)

Step-by-step explanation:

Step 1: Rearrange expression

sin(π/3)cos(π/7) - cos(π/3)sin(π/7)

Step 2: Use sin(A ± B)

sin(π/3 - π/7)

Step 3: Evaluate

sin(4π/21)

And we have our answer!


Related Questions

-3(-5x-2u+1) use the distributive property to remove the parentheses

Answers

Answer:

15x+6u−3

Step-by-step explanation:

This means -3 times -5x, -3 times -2u, and -3 times 1.

Do this and you have, 15x+6u-3.

A TV studio has brought in 8 boy kittens and 9 girl kittens for a cat food commercial. The director is going to choose 11 of these kittens at random to be in the commercial. What is the probability that the director chooses 4 boy kittens and 7 girl kittens? Round your answer to three decimal places.

Answers

Answer:

0.204

Step-by-step explanation:

The formula to use to solve this is the combination formula.

Combination formula =

C(n, r) = nCr = n!/r! (n - r)!

Total number of kittens = 8 boy kittens + 9 girl kittens

= 17 kittens

Step 1

We find the probability of choosing 4 boy kittens out of 8 boy kittens

= 8C4 = 8!/4! × (8 - 4)!

= 8C4 = 8! / 4! × 4!

= 8C4 = 8 × 7 × 6 × 5 × 4 × 3 × 2 × 1/ (4 × 3 × 2 × 1) × (4 × 3 × 2 × 1)

8C4 = 70

Step 2

We find the probability of choosing 7 girl kittens out of 9 girl kittens

9C7 = 9!/7! × (9 - 7)!

= 9C7 = 9! / 7! × 2!

= 9C7 = 9 × 8 × 7 × 6 × 5 × 4 × 3 × 2 × 1/ (7 × 6 × 5 × 4 × 3 × 2 × 1) × (2 × 1)

9C7 = 36

Step 3

Find the probability of Picking 11 kittens out of 17 kittens

17C11 = 17!/11! × (17 - 11)!

= 17C11 = 17! / 11! × 6!

= 17C11 = 17 × 16 × 15 × 14 × 13 × 12 × 11 × 10 × 9 × 8 × 7 × 6 × 5 × 4 × 3 × 2 × 1/ (11 × 10 × 9 × 8 × 7 × 6 × 5 × 4 × 3 × 2 × 1) × (6 × 5 × 4 × 3 × 2 × 1)

17C11 = 12,376

Step 4

The final step

The probability that the director chooses 4 boy kittens and 7 girl kittens

= 8C4 × 9C7/ 17C11

= 70 × 36/12376

= 2520/12376

= 0.2036199095

Approximately to 3 decimal places = 0.204

Therefore, the probability that the director chooses 4 boy kittens and 7 girl kittens is 0.204

on tuesday, david picked a apples each hour for 5 hours, and elanor picked b apples each hour for 8 hours. which of the following represents the total number of apples picked by david and elanor on tuesday? a) 13ab b) 40ab c) 5a + 8b d) 8a + 5b

Answers

Answer:

c) 5a + 8b

Step-by-step explanation:

[tex]a \: apples = 1 \: hours\\x \: apples = 5 \: hours\\x = 5a\\Total \:no \:of \:apples \:picked\\\:by \:david \:= 5a\\\\\\b \:apples = 1 \:hour\\x \:apples = 8 hours\\x = 8b\\Total \:no \:of \:apples \:picked\\ \:by \:elanor = 8b\\\\Total \:no \:of \:Apples =5a+8b[/tex]

a theater has (2x+1) rows of seats, with (x-3) seats in each row. how many seats are in the theater?
A. 2x^2- 5x- 3
B. 2x^2+ 5x- 3
C. 2x^2- 7x+ 3
D. 2x^2- 7x- 3

Answers

the answer would be B hope it’s right

(2x+1)(x-3)

y(x-3) .... let y = 2x+1

y*x+y(-3) .... distribute

xy - 3y

x( y ) - 3( y )

x( 2x+1 ) - 3( 2x+1) ... replace y with 2x+1

2x^2 + x - 6x - 3 ..... distribute

2x^2 - 5x - 3

Answer is choice A

Let T (x, y) = (x + 1, y + 1) and S (x, y) = (x + 5, y + 4). In what
quadrant is S (T (P)) when P(-7, 1)?

Answers

Answer:

quadrant 2

Step-by-step explanation:

10 - 2x, when x = 3

Answers

Answer:

4

Step-by-step explanation:

Plug in 3 as x in the expression:

10 - 2x

10 - 2(3)

10 - 6

= 4

Answer:

4

Step-by-step explanation:

10 - 2x

Let x =3

10 -2(3)

10 -6

4

Noel pays $1.54 in sales tax.The sales tax rate is 5.5%,what the original price

Answers

Step-by-step explanation:

Hi, there!!!

Let's simply work with it,

Here,

tax=$1.54

rate of tax= 5.5%

now, let the original price be x.

so, 5.5% of x= $1.54 { tax amount = tax% of original price}.

or, 5.5/100 × x= $1.54

or, 5.5x = $1.54×100

or, x= $28.

Therefore, the original price was $28.

Hope it helps...

How hot does it get in Death Valley? The following data are taken from a study conducted by the National Park System, of which Death Valley is a unit. The ground temperatures (°F) were taken from May to November in the vicinity of Furnace Creek. Compute the mean, median, and mode for these ground temperatures. (Enter your answers to one decimal place.) 147 153 170 172 185 181 182 185 181 170 181 167 153 145

Answers

Answer:

Mean: 169.4

Median: 171

Mode: 181

Step-by-step explanation:

I first sorted the numbers by value, least to greatest.

145 147 153 153 167 170 170 172 181 181 181 182 185 185

We can see that 181 occurs the most, 3 times, so it's the mode.

The median of this set will be the middle number(s).

When we take away 6 numbers from both sides we are left with 170 and 172, and the mean of these two numbers is 171. So the median is 171.

We can add all the numbers and divide by 14 to get the mean.

[tex]147+153+170+172+185+181+182+185+181+170+181+167+153+145=2372\\\\2372\div14\approx169.4[/tex]

Hope this helped!

CALC 1: Spud's mom is going to make him a round birthday cake, and has asked for your help. Spud is a bit weird, and has already
announced that when he slices the cake, your slice will have a perimeter of 16 inches, because you're his favorite friend, and
that's his favorite number. Since you're helping his mom with the baking, what diameter cake will you recommend she makes
so that you end up with the most possible cake at weird Spud's party? (Hint: you can ignore the thickness df the cake, since
this will be the same, regardless of its diameter.)
10.1
in

Answers

Answer:

15.7 in  

Step-by-step explanation:

A slice of a round pie is a sector of a circle.

The perimeter of a slice is the arc length s plus twice the radius r.

P = s + 2r

s = rθ = r(16/360) = r/22.5. So,

16 = (r/22.5) + 2r = (r + 45r)/22.5 = 46r/22.5

16 × 22.5 = 46r

360 = 46r

r = 7.826  

D = 2r = 2 × 7.826 = 15.7 in

The diameter of the cake should be 15.7 in.

Check:

[tex]\begin{array}{rcl}P & = & s + 2r\\& = & \dfrac{r}{22.5} + 2r\\\\16 & = & \dfrac{7.826}{22.5} + 2 \times 7.826\\\\16 & = & 0.35 + 15.65\\16 & = & 16.00\\\end{array}[/tex]

It checks.

 

A research center is interested in investigating the height and age of children who are between 5 to 9 years old. In order to do this, a sample of 15 children is selected and the data are given below.


Age (in years) Height (inches)

7 47.3

8 48.8

5 41.3

8 50.4

8 51

7 47.1

7 46.9

7 48

9 51.2

8 51.2

5 40.3

8 48.9

6 45.2

5 41.9

8 49.6


Requried:

a. Develop a scatter chart with age as the independent variable. What does the scatter chart indicate about the relationship between the height and age of children?

b. Use the data to develop an estimated regression equation that could be used to estimate the height based on the age. What is the estimated regression model?

c. How much of the variation in the sample values of height does the model estimated in part (b) explain?

Answers

Answer:

Kindly check explanation

Step-by-step explanation:

Given the data:

Age(x)

7

8

5

8

8

7

7

7

9

8

5

8

6

5

8

Height (Y)

47.3

48.8

41.3

50.4

51

47.1

46.9

48

51.2

51.2

40.3

48.9

45.2

41.9

49.6

The estimated regression equation:

ŷ = 2.73953X + 27.91395

Where ;

X = independent variable

ŷ = predicted or dependent variable

27.91395 = intercept

C.) To obtain the variation in sample values of height estimated by the model, we obtain the Coefficient of correlation:

Using the online pearson correlation Coefficient calculator :

The correlation Coefficient is 0.9696.

which means that the regression model estimated in part (b) explains approximately (0.9696 * 100) = 96.96% = 97% of the variation in the height in the sample.

help please precalc will give brainliest

Answers

In part (D), we found

[tex]2\sin(4\pi t)+5\cos(4\pi t)=\sqrt{29}\sin\left(4\pi t+\tan^{-1}\left(\dfrac52\right)\right)[/tex]

so the phase [tex]\phi[/tex] is [tex]\tan^{-1}\left(\frac52\right)\approx1.19\,\rm rad[/tex], which falls between 0 and [tex]\frac\pi2[/tex]. This means the weight is somewhere between the maximum positive position (where [tex]\phi[/tex] would be 0) and the equilibrium position (where [tex]\phi[/tex] would be [tex]\frac\pi2[/tex]), and would be traveling in the negative direction.

Which is the exponential form of log9 5 = y

Answers

Answer:

Step-by-step explanation:

[tex]\log _9\left(5\right)=y\\y=\log _9\left(5\right)[/tex]

70% of what number is 56​

Answers

Answer:80
Because we do the inverse so 56*10=560 then we do 560/7=80 then we work from 80 and do 70% to see if our answer is right
Hope this helped

Answer:

the number is 80

Step-by-step explanation:

let x be an unknown number so from the above question we deduce that

(70/100)*x=56

70x/100=56

70x=56*100

70x=5600

70x/70=5600/70

x=80

John receives a perpetuity paying 2 at the end of year 4, 4 at the end of year 6, 6 at the end of year 8, etc. The present value of this perpetuity at an annual effective rate of 10% equals X. Calculate X

Answers

Answer:

45.35

Step-by-step explanation:

From the above question, we are told that the annual effective rate = 10% = 0.10

Note also that payment is been made every 2 years

Hence , we apply the formula of effective interest rate for a period of 2 years.

Effective Interest rate(j) = (1 + r)² - 1

= (1 + 0.10)² - 1

= 1.10² - 1

= 1.21

= 0.21

Present value of perpetuality = t/[j × j/(1 + r)²]

Where t = time in years = 2

r = 0.10

= 2/ [0.21 × 0.21/(1 + 0.10)²

= 54.87528

Present value at time t = 0

= 54.87528(1 + r)^-2

= 54.87528(1 + 0.10) ^-2

= 54.87528(1.10)^-2

= 45.35

Therefore, the present value at time (t) is 0 = 45.35

I really need help here I am super confused
Which of the following steps can be performed so that the square root property may easily be applied to 2x^2=16?(1 point)
The square root property requires a quantity squared by itself on one side of the equation. The only quantity squared is​ 16, so divide both sides by 2 before applying the square root property.
The square root property requires a quantity squared by itself on one side of the equation. The only quantity squared is​ x, so divide both sides by 2 before applying the square root property.
The square root property requires a quantity squared by itself on one side of the equation. The only quantity squared is​ 16, so divide both sides by 16 before applying the square root property.
The square root property requires a quantity squared by itself on one side of the equation. The only quantity squared is​ x, so divide both sides by 16 before applying the square root property.
Which of the following steps would not be necessary when using the square root property to solve a quadratic​ equation?(1 point)
The square root property may be applied only if the constant is positive.
Isolate the quantity being squared.
After applying the square root​ property, solve the resulting equations. When taking the square root of both​ sides, use ± on the square root of the constant.

Answers

Answer:

The square root property requires a quantity squared by itself on one side of the equation. The only quantity squared is​ x, so divide both sides by 2 before applying the square root property.

Step-by-step explanation:

In the above question, we are given the expression: 2x^2=16 and we are asked the proper way to apply the square root property.

2x² = 16 is an algebraic equation

To apply square root property to an expression, there must be only one quantity that is squared.

Step 1

We divide both sides by 2

This is because we have to first eliminate the coefficient of x

2x²/2 = 16/2

x² = 8

Step 2

Now that we have eliminated the coefficient of x², we can apply the square root property now because x is the only quantity that is squared.

√x² = √8

x = √8

Therefore, Option 2 which says: "The square root property requires a quantity squared by itself on one side of the equation. The only quantity squared is​ x, so divide both sides by 2 before applying the square root property." is the correct option

The report "Teens and Distracted Driving: Texting, Talking and Other Uses of the Cell Phone Behind the Wheel" summarizes data from a survey of a representative sample of 800 teens between the ages of 12 and 17. The following statements were made on the basis of the resulting data.

- 75% of all American teens own a cellphone
- 66% of all American teens use a cellphone to send a receive text messages
- 26% of American teens age 16-17 have used a cellphone to text while driving

Required:
a. Is the inference made one that involves estimation or one that involved hypothesis testing?
b. What is the population of interest? American teenagers? American teenagers between ages 12-17? Americans? Teenagers?

Answers

Answer:

"Teens and Distracted Driving: Texting, Talking and Other Uses of the Cell Phone Behind the Wheel"

a. The inference made involves estimation.  The question provided that the statements were made on the basis of the resulting data and not on the basis of some hypothesis testing.

This implies that some statistics were calculated from sample data to approximate the population parameter, as shown in the statements.  The statements were not an attempt to establish the statistical significance of some claims.

b. The population of interest is American teenagers between 12-17.

Step-by-step explanation:

An inference from data is a statistical estimation by which some statistics are calculated based on the sample data of 800 teens between the ages of 12 and 17.  The statistics serve as an approximation to the population parameter.

Inference based on hypothesis testing establishes if a claim has statistical significance by providing  statistical evidence in favor of the claim or against it.

3 ratios that are equivalent to 6:12

Answers

Answer:

1:3

2:4

3:6

Step-by-step explanation:

we can divide both sides by 6 and get 1:2

we can divide both sides by 3 and get 2:4

we can divide both sides by 2 and get 3:6

Answer:

12:24, 3:6, 2:4

Step-by-step explanation:

What we are looking for here is a ratio that, when you divide/multiply the same constant on both parts of the ratio, you get 6:12.

6:12 is the same thing as 1:2, so we can find ratios equivalent to 1:2 (the first value will be half the second).

Hope this helped!

Bette had 280 kilograms of bolts and put the same amount into each of 8 boxes. How
much will the bolts weigh in each box?

Answers

Answer:

35

Step-by-step explanation:

You have to divide 280 by 8 and that's how you get it.

A sample of 31 observations is selected from a normal population. The sample mean is 11, and the population standard deviation is 3. Conduct the following test of hypothesis using the 0.05 significance level. H0: μ ≤ 10 H1: μ > 10 Is this a one- or two-tailed test?

Answers

Answer:

The  test is a two -tailed test

Step-by-step explanation:

From the question we are told that

    The  sample size is n  =  31

     The  sample mean is  [tex]\= x =11[/tex]

      The sample standard deviation is  [tex]\sigma = 3[/tex]

       The null hypothesis is  [tex]H_o: \mu \le 10[/tex]

         The  alternative hypothesis is  [tex]H_1 : \mu > 10[/tex]  

         The level of significance is [tex]\alpha = 0.05[/tex]

 

The test  statistics is mathematically represented as

       [tex]t = \frac{ \= x - \mu }{ \frac{\sigma }{\sqrt{n} } }[/tex]

substituting values

      [tex]t = \frac{ 11 - 10 }{ \frac{3}{\sqrt{ 31} } }[/tex]

     [tex]t = 1.85[/tex]

The  p- value is mathematically represented as

       [tex]p-value = p( t > 1.856) = 0.0317[/tex]

Looking at the value of  [tex]p-value \ and \ \alpha[/tex] we see that [tex]p-value < \alpha[/tex] hence we reject the null hypothesis

Given the that the p value is less than 0.05 it mean the this is a two-tailed test

Evan’s dog weighs 15 3/8 pounds. What is this weight written as a decimal? A. 15.125 Ib B. 15.375 Ib C. 15.385 Ib D. 15.625 Ib Please include ALL work!

Answers

Answer:

ok as we know 15 is a whole number by itself and 3/8 is the decimal part

so we know it is 15. something

that something is 3/8 to find decimal you do 3/8

3/8 is = .375

so 15.375 is the answer

hope it helps

brainliest give me pls

What is the area of the region bounded by the three lines with equations $2x+y = 8$, $2x-5y = 20$ and $x+y = 10$?

Answers

Answer:

  42

Step-by-step explanation:

A graphing tool is useful for finding the points of intersection of these lines. If the equations are numbered 1, 2, 3 in the order given, we can find the points of intersection to be ...

  equations 1, 2: A(5, -2)

  equations 2, 3: B(10, 0)

  equations (3, 1): C(-2, 12)

Then the area can be found from the coordinates using the formula ...

  A = (1/2)|x1(y2-y3) +x2(y3-y1) +x3(y1-y2)|

  = (1/2)|5(0-12) +10(12-(-2)) -2(-2-0))| = (1/2)|-60 +140 +4|

  A = 42

The area of the triangular region is 42 square units.

The average of 4 numbers is 15 , the sum of 3 numbers is 14 what is the fourth number

Answers

Answer:

46

Step-by-step explanation:

(14+x)/4 = 15

14 + x = 60

x = 46

Answer:

46

Step-by-step explanation:

Let a to d be number 1 to 4 respectively.

15 = (a + b + c + d) / 4

(a + b + c + d) = 60 ------> total sum of the 4 numbers

Since the sum of 3 numbers (assuming a to c) is 14,

Fourth number (d) = 60 - 14

= 46

That's how I would do it, hope this helps :)

I NEED FULL EXPLANATION

(4 - 3i) ^2

Answers

Answer:

Rewrite  

( 4 − 3 i ) 2  as  ( 4 − 3 i )( 4 − 3 i ) . ( 4 − 3 i) ( 4 − 3 i ) Expand  ( 4 − 3 i ) ( 4 − 3 i )

using the FOIL Method.

4 ⋅ 4 + 4 ( -3 i ) − 3 i ⋅ 4 − 3 i ( − 3 i )

Simplify and combine like terms.

7 − 24 i

Step-by-step explanation:

Answer:

7 -24i

Step-by-step explanation:

(4 - 3i) ^2

(4-3i) * (4-3i)

FOIL

first 4*4 = 16

outer 4 * -3i = -12i

inner -3i *4 = -12i

last -3i*-3i = 9i^2 = 9 (-1) = -9

Add together

16 -12i-12i -9

Combine like terms

7 -24i

A refrigeration system at your company uses temperature sensors fixed to read Celsius (0C) values, but the system operators in your control room understand only the Fahrenheit scale. You have been asked to make a Fahrenheit (°F) label for the high temperature alarm, which is set to ring whenever the system temperature rises above -10°C. What Fahrenheit value should you write on the label?

Answers

Answer:

14 °F

Step-by-step explanation:

To answer this problem, we will use the known celsius to fahrenheit conversion formula.

[Celsius * (9/5)] + 32 = Fahrenheit

Now we just plug in the value of celsius:

[-10 * (9/5)] + 32 = Fahrenheit

[ -2 * 9 ] + 32 = Fahrenheit

[ -18 ] + 32 = Fahrenheit

14 = Fahrenheit

So you should right 14(°F) on the label.

Cheers.

Scores on a University exam are normally distributed with a mean of 68 and a standard deviation of 9. Using the 68-95-99.7 rule, what percentage of students score above 77?

Answers

Answer:

0.1585, or 15.85%

Step-by-step explanation:

On a standard bell curve, the area from 77 to 100 falls within the 95.45 to 99.73 range.

99.73 - 68.27 = 31.46

31.46 / 2 =15.73

99.7 - 68 = 31.7

31.7 / 2 = 15.85

] You are scheduled to receive $20,000 in two years. When you receive it, you will invest it for six more years at 8.4 percent per year. How much will you have in eight years?

Answers

Answer:

32449.3

Step-by-step explanation:

use the formula A = P(1+r / 100)^t

20000 × (1+ (8.4 / 100))^6

=32449.3

A restaurant hands out a scratch-off game ticket with prizes being worth purchases at the restaurant. The back of the ticket lists the odds of winning each dollar value: 0.05 for $10, 0.04 for $25, 0.01 for $50, and 0.003 for $100. What are the odds that the ticket is worth at least $25?

Answers

Answer: 0.05412

Step-by-step explanation:

Formula : Odds of having an event is given by  [tex]o=\dfrac{p}{1-p}[/tex], where p = probability that event happens.

In terms to find p , we use [tex]p=\dfrac{o}{1+o}[/tex]

Given, he back of the ticket lists the odds of winning each dollar value: 0.05 for $10, 0.04 for $25, 0.01 for $50, and 0.003 for $100.

Let X be the worth of ticket.

Then, the probability that the ticket is worth at least $25 =

[tex]P(X\geq 25)=P(X=25)+P(X=50)+P(X=100)[/tex]

[tex]=\dfrac{0.04}{1+0.04}+\dfrac{0.01}{1+0.01}+\dfrac{0.003}{1+0.003}\\\\=0.05135[/tex]

The odds that the ticket is worth at least $25 = [tex]\dfrac{0.05135}{1-0.05135}[/tex]

=0.05412

hence, the odds that the ticket is worth at least $25 is 0.05412 .

What's the solution of the following linear system? 5x + 2y = 9 –5x – 2y = 3

Answers

━━━━━━━☆☆━━━━━━━

▹ Answer

(-39/35, 9/7)

▹ Step-by-Step Explanation

5y + 2y = 9

-5x - 2y = 3

Solve the equation:

y = 9/7

-5x - 2y = 3

Substitute the value of y:

-5x - 2 * 9/7 = 3

x = -39/35

(x, y) = (-39/35, 9/7)

Hope this helps!

CloutAnswers ❁

━━━━━━━☆☆━━━━━━━

5x + 2y = 9-5x - 2y = 3

To solve this system by addition, we start by adding both of our equations together but notice that the x terms and the y terms cancel out.

This leaves us with 0 on the left side and on the right side,

9 + 13 = 12 so we are left with the equation 0 = 12.

Since 0 = 12 is a false statement, this means that

there is no solution to our system of equations.

Select the correct answer from each drop-down menu.
Nirja has 24 marbles. The number of marbles Nirja has is 6 more than the number of marbles Tim has.
If Tim has x marbles, the equation that represents the situation is
The value of x that makes the equation true is
Reset
Next

Answers

Answer:

24 = x+6

x = 18

Step-by-step explanation:

N = 24

T = x

N = x+6  

24 = x+6

Subtract 6 from each side

24-6 = x+6-6

18 = x

Time has 6 marbles

Nirja has 6 more than Tim,

So you can subtract 6 from 24 to find x:

24-6 = x

Or you can add 6 to x to equal 24:

x + 6 = 24

You don't list the choices but it should be one of these.

Solve:

24 - 6 = x

x = 18

PLEASE HELP!!!!!! TIMED QUESTION!!!! FIRST CORRECT ANSWER WILL GET BRAINLIEST....PLEASE ANSWER NOW!!!!

The bar graph shows the number of students who earned each letter grade on an
exam, which statement about the graph is true?

1)
1/5 of the students earned a C
2)
3% more students earned an A then B
3)
20% of the students earned a D
4)
1/4 of the class earned a B

Answers

Answer:

Option (3)

Step-by-step explanation:

From the picture attached,

Bar graph sketched shows the grades earned by the students in an exam.

Number of students who achieved the grade A = 17

Number of students who achieved grade B = 14

Number of students with grade C = 5

Number of students with grade D = 9

Total students who took the exam = 17 + 14 + 5 + 9 = 45

Option (1)

"[tex]\frac{1}{5}[/tex] of the students earned a C"

Fraction of students who earned C = [tex]\frac{\text{Students who earned C}}{\text{Total students}}[/tex]

                                                          = [tex]\frac{5}{45}[/tex]

                                                          = [tex]\frac{1}{9}[/tex]

Therefore, this option is incorrect.

Option (2)

"3% more students earned an A then B"

Percentage of students who earned A = [tex]\frac{\text{Students got A}}{\text{Total students who took the exam}}\times 100[/tex]

                                                                = [tex]\frac{17}{45}\times 100[/tex]

                                                                = 37.78%

Percentage of students who earned B = [tex]\frac{\text{Students got B}}{\text{Total students who took the exam}}\times 100[/tex]

                                                                = [tex]\frac{14}{45}\times 100[/tex]

                                                                = 31.11%

Difference in percentage = 37.78 - 31.11

                                          = 6.67%

Therefore, this option is not correct.

Option (3)

"20% of the students earned a D"

Percentage of students who earned D = [tex]\frac{\text{Students got D}}{\text{Total students who took the exam}}\times 100[/tex]

                                                                 = [tex]\frac{9}{45}\times 100[/tex]

                                                                 = 20%

Option (3) is the correct option.

Option (4)

" [tex]\frac{1}{4}[/tex] of the class earned a B"

Fraction of class who earned B = [tex]\frac{\text{Students got B}}{\text{Total students who took the exam}}[/tex]

                                                    = [tex]\frac{14}{45}[/tex]

Therefore, Option (4) is not correct.                                        

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