Answer:
simply convert first feets into miles
Given is 5280 feets=1 miles
63756 /5280=12.075 miles
70 minutes = 1.16666= 1.17 hrs
rate is 12.075 miles/1.17 hrs
Step-by-step explanation:
i need help asap please
Answer:
[tex]x = -\frac{3}{2}[/tex] or [tex]x = 1[/tex]
Step-by-step explanation:
Using the zero product property, first step is to set the given equation, [tex] 2x^2 + x - 1 = 2 [/tex] , to zero. Then factorise the left side.
Thus,
[tex] 2x^2 + x - 1 = 2 [/tex]
Subtract 2 from both sides
[tex] 2x^2 + x - 1 - 2 = 2 - 2 [/tex]
[tex] 2x^2 + x - 3 = 0 [/tex]
Factorise the left side
[tex] 2x^2 + 3x - 2x - 3 = 0 [/tex]
[tex] x(2x + 3) - 1(2x + 3) = 0 [/tex]
[tex] (x - 1)(2x + 3) = 0 [/tex]
Find the solution
[tex] x - 1 = 0 [/tex]
Or
[tex]2x + 3 = 0[/tex]
[tex] x = 1 [/tex]
Or
[tex]2x + 3 = 0[/tex]
[tex]2x = -3[/tex]
[tex]x = -\frac{3}{2}[/tex]
The answer is: [tex] x = 1 [/tex] or [tex]x = -\frac{3}{2}[/tex]
(4x2y3)2=? thank you for the help
Answer:
Step-by-step explanation:
2 3x2y3
(SAT Prep) Find the value of x.
Answer:
The value of x is 30°
Step-by-step explanation:
We are given that the outer angle of the parallelogram is 60 degrees. Therefore it's respective inner angle will be 180 - 60 = 120 degrees. And, by properties of a parallelogram, the angle opposite to this angle will be 120 degrees as well.
If we draw extend the line creating angle 2x, then we will make ( 1 ) a vertical angle to 2x, ( 2 ) a 90 degree angle, and ( 3 ) and angle that we can let be y. Therefore, 2x + y = 90, and 3x + y = 120.
[tex]\begin{bmatrix}2x+y=90\\ 3x+y=120\end{bmatrix}[/tex] ,
[tex]\begin{bmatrix}6x+3y=270\\ 6x+2y=240\end{bmatrix}[/tex] ,
[tex]6x+2y=240\\-\\\underline{6x+3y=270}\\y=30[/tex],
[tex]2x + (30) = 90,\\2x = 60,\\x = 30[/tex]
Solution : x = 30°
Answer:
x = 30
Step-by-step explanation:
a+ 60 = 180
a = 120
3x+b = 120 because opposite angles in a parallelogram are equal
2x+90+b = 180 since it forms a line
2x+b = 90
We have 2 equations and 2 unknowns
3x+b = 120
2x+b = 90
Subtracting
3x+b = 120
-2x-b = -90
---------------------
x = 30
Common ratio 2/3, -2, 6
Answer:
The common ratio is - 3Step-by-step explanation:
To find the common ratio between the terms of the sequence divide the previous term by the next term.
That's
[tex] - 2 \div \frac{2}{3} = - 2 \times \frac{3}{2} = - 3[/tex]Or
[tex] \frac{6}{ - 2} = - 3[/tex]Therefore the common ratio of the sequence is - 3
Hope this helps you
Answer:
-3
Step-by-step explanation:
You are an urban planner assessing the growth of a city. Ten years ago, the city's population was 250,823. Its current population is 325,823. By about what percentage has the city grown over the past ten years? Round to the nearest percent.
Answer:
Here is the answer i got-
Step-by-step explanation:
325823-250823=75000
325823’s 244367250percent is 75000
Find the limit. Use l'Hospital's Rule where appropriate. If there is a more elementary method, consider using it. lim x→9 x − 9 x2 − 81
Without resorting to L'Hopitâl's rule,
[tex]\displaystyle\lim_{x\to9}\frac{x-9}{x^2-81}=\lim_{x\to9}\frac{x-9}{(x-9)(x+9)}=\lim_{x\to9}\frac1{x+9}=\frac1{18}[/tex]
With the rule, we get the same result:
[tex]\displaystyle\lim_{x\to9}\frac{x-9}{x^2-81}=\lim_{x\to9}\frac1{2x}=\frac1{18}[/tex]
PLEASE HELP!!!!!!
Look at the triangle ABC.
A (4.5)
5
4
3
2
1
C (4.1)
B (2.1)
1 2 3
4 5
--5 -4 -3 -2 -1 0
-1
-2
-3
-4
-5
What is the length of the side AB of the triangle?
2
20
38
=========================================
Explanation:
Count out the spaces, or use subtraction, to find the horizontal side BC is 2 units long. Similarly, you'll find the vertical side AC is 4 units long.
Use the pythagorean theorem to find the length of segment AB.
a^2 + b^2 = c^2
2^2 + 4^2 = c^2
4 + 16 = c^2
20 = c^2
c^2 = 20
c = sqrt(20)
We stop here since it matches with choice B.
-----------------
Optionally, we can simplify like so
sqrt(20) = sqrt(4*5)
sqrt(20) = sqrt(4)*sqrt(5)
sqrt(20) = 2*sqrt(5)
Answer:
The answer is [tex]\sqrt{20}[/tex].
Step-by-step explanation:
Use the Pythagorean Theorem.
[tex]2^{2} + 4^{2} = c^{2} \\4+16 = c^{2} \\\sqrt{20} = c[/tex]
What is the opposite of the opposite of negative 52?
Answer:
-52
Step-by-step explanation:
Think of it this way. Opposite means to take the negation. So we are taking the negation of the negation of negative 52. This means mathematically:
- ( - ( -52 ) ) == -52
Cheers.
Determine that 4/16 and 5/20 forms as proportional relationship.
Answer:
Those two are 0.25
4/16 = 1/4
5/20 = 1/4
Answer: Please Give Me Brainliest, Thank You!
4/16 = 5/20 = 1/4
Step-by-step explanation:
Because If you divide 4 and 16 by 4 you get 1/4 and if you divide 5 and 20 with 5 you get 1/4
Find the interest on a Principal Balance of $10,000 over the course of eight years with an interest rate of 5.5%. Do this for: Simple Interest.
Answer:
Simple Interest : $ 4400
Step-by-step explanation:
We want to calculate the interest on $ 10,000, at 5.5% interest rate per year, over a course of 8 years.
We can use the simple interest formula here, or :
I = P × r × t,
Where P is the principle amount, $ 10,000, r is the interest rate, 5.5% each year, or in decimal form 5.5 / 100 = 0.055. t is the time, 8 years.
Simple Interest : 10000 × 0.055 × 8 = $4400.00
Then again the interest can be added to the principal amount ( $10,000 ) to receive some new amount after 8 years, which is $ 14,000. However the simple interest earned in 8 years at a rate of 5.5% should be $4400.
The simple interest earned on the amount is $4,400
Interest is the total amount that would be paid or earned from making an investment or taking a loan over a period of time.
Simple Interest = principal x time x interest rate
principal = amount borrowed = $10,000
time = 8 years
Interest rate = 5.5%
10,000 x 0.055 x 8 = $4,400
To learn more about simple interest, please check: https://brainly.com/question/9352088?referrer=searchResults
Simplify -2x^3 y x xy^2
Answer:
(4,4)⋅(4,4)
Step-by-step explanation:
Sodas in a can are supposed to contain an average 12 oz. This particular brand has a standard deviation of 0.1 oz, with an average of 12.1 oz. If the can’s contents follow a Normal distribution, what is the probability that the mean contents of a six-pack are less than 12 oz?
Answer:
The probability is [tex]P(X < 12) = 0.99286[/tex]
Step-by-step explanation:
From the question we are told that
The population mean is [tex]\mu = 12 \ oz[/tex]
The standard deviation is [tex]\sigma = 0.1 \ oz[/tex]
The sample mean is [tex]\= x = 12.1 \ oz[/tex]
The sample size is n = 6 packs
The standard error of the mean is mathematically represented as
[tex]\sigma_{\= x } = \frac{\sigma}{\sqrt{n} }[/tex]
substituting values
[tex]\sigma_{\= x } = \frac{0.1}{\sqrt{6} }[/tex]
[tex]\sigma_{\= x } = 0.0408[/tex]
Given that the can’s contents follow a Normal distribution then then the probability that the mean contents of a six-pack are less than 12 oz is mathematically represented as
[tex]P(X < 12) = P ( \frac{X - \mu }{ \sigma_{\= x }} < \frac{\= x - \mu }{ \sigma_{\= x }} )[/tex]
Generally [tex]\frac{X - \mu }{ \sigma_{ \= x }} = Z (The \ standardized \ value \ of \ X )[/tex]
So
[tex]P(X < 12) = P ( Z < \frac{\= x - \mu }{ \sigma_{\= x }} )[/tex]
substituting values
[tex]P(X < 12) = P ( Z < \frac{12.2 -12 }{0.0408} )[/tex]
[tex]P(X < 12) = P ( Z < 2.45 )[/tex]
From the normal distribution table the value of [tex]P ( Z < 2.45 )[/tex] is
[tex]P (Z < 2.45)0.99286[/tex]
=> [tex]P(X < 12) = 0.99286[/tex]
GIVING OUT BRAINLIEST TO THE FIRST PERSON WHO ANSWERS!! I would appreciate if if you do answer though! <3
Also, include ALL work!
Answer:
The answer is option BStep-by-step explanation:
Total number of people = 800
To find the number of unemployed people we must first find the total percentage of the pie chart
That's
25 + 10 + 5 + 60 = 100%
5 % out of the 100% are unemployed
To find the number of unemployed people divide 5 % by the total percentage that's 100% and multiply them by the total number of people
That's
[tex] \frac{5}{100} \times 800[/tex]
5 × 8
We have the final answer as
40 peopleHope this helps you
A plan for a dog park has a grassy section and a sitting section as shown in the figure. Which equation can be used to find the area of the grassy section?
Answer:
length times width
Step-by-step explanation:
plzzz help me quick will give goood rate
Answer:
Average rate of change of the function will be = (-1.5)
Step-by-step explanation:
Average rate of change of a function f(x) is determined by the formula,
Average rate of change = [tex]\frac{f(b)-f(a)}{b-a}[/tex] If a < x < b
We have to find the average rate of change of a function g(t) between the interval [-3, 1]
From the given table,
For t = -3,
g(-3) = 6
For t = 1,
g(1) = 0
Therefore, average rate of change of the function in the given interval
= [tex]\frac{g(1)-g(-3)}{1-(-3)}[/tex]
= [tex]\frac{0-6}{1+3}[/tex]
= [tex]-\frac{3}{2}[/tex]
= - 1.5
g When conducting a one-way ANOVA, the _______ the between-treatment variability is when compared to the within-treatment variability, the __________the value of the F statistic will be which gives us ________ evidence against the null. (Choose all that apply)
Answer:
One - way ANOVA, the smaller the between treatment
The smaller the value of F statistic will give us significant evidence.
Step-by-step explanation:
ANOVA is a statistical technique designed to test mean of one or more quantitative populations. In two-way ANOVA it equals the block mean. Column block means square is three-way ANOVA. It is a statistical technique designed to test mean of one or more quantitative populations. In two-way ANOVA it equals the block mean. Column block means square is three-way ANOVA.
One-way ANOVA, the smaller the between treatment
The smaller the value of F statistic will give us significant evidence.
What is ANOVA?It should be the statistical technique that are made for testing the mean for one or more than one quantitative population. In two-way ANOVA it should be equivalent to the block mean. Here the column block represent the square be the three-way ANOVA.
Therefore, One-way ANOVA, the smaller the between treatment
The smaller the value of F statistic will give us significant evidence.
Learn more about evidence here: https://brainly.com/question/6764645?referrer=searchResults
Jessica is at a charity fundraiser and has a chance of receiving a gift. The odds in favor of receiving a gift are 5/12. Find the probability of Jessica receiving a gift.
Answer:
5/17
Step-by-step explanation:
This is a question to calculate probability from odds. The formula is given as:
A formula for calculating probability from odds is P = Odds / (Odds + 1)
From the question , we are told that the odds of receiving a gift is
= 5:12
The probability of Jessica receiving a gift =
Probability = Odds / (Odds + 1)
P = 5/12 / ( 5/12 + 1)
P = (5/12)/ (17/12)
P = 5/12 × 12/17
= 5/17
Therefore, the probability of Jessica. receiving a gift is 5/17.
What is the error in this problem
Answer:
The angle of elevation is not properly represented
Step-by-step explanation:
Given
The question in the attachment;
Required
Determine the error
See attachment for proper representation of the angle of elevation;
Solving further (From the Attachment)
[tex]Tan22 = \frac{x}{3000}[/tex]
Multiply both sides by 3000
[tex]x = 3000 * tan22[/tex]
[tex]x = 3000 * 0.4040[/tex]
[tex]x = 1212[/tex]
The cliff is about 1212 feet high
A mutual fund owns 20,000 shares in Company Y. Company Y has 2 million shares issued. In one particular year, Company Y announces annual profits of $6 million, and decides to pay dividends to its shareholders at a rate of 15% of its annual profits. How much will the mutual fund receive in the form of dividends from Company Y? Round your answer to the nearest dollar.
Answer: $9,000
Step-by-step explanation:
Step 1
Calculate the amount of dividends the company will pay to all its shareholders.
= 15% of profits
= 15% * 6,000,000
= $900,000
Step 2
Calculate how much dividends each share will get;
$900,000 to 2 million shares of Company Y.
= 900,000/2,000,000
= $0.45
Step 3
Calculate how much the Mutual fund will get for its 20,000 shares
= 20,000 * 0.45
= $9,000
A number is chosen at random from 1 to 10. Find
the probability of selecting 4 or a factor of 6.
Step by step.
Answer:
1/2
Step-by-step explanation:
The possible outcomes are
1,2,3,4,5,6,7,8,9,10
Factors of 6 are 1,2,3,6
or a 4
1,2,3,4,6 are the outcomes we want
There are 5 "good" outcomes
P( 4 or a factor of 6) = "good" outcomes/ total
= 5/10
=1/2
Answer:
[tex]\boxed{\frac{1}{2} }[/tex]
Step-by-step explanation:
There are total 10 outcomes.
[tex]1,2,3,4,5,6,7,8,9,10[/tex]
The probability of selecting 4 is 1 outcome out of total 10 outcomes.
Factors of 6 are [tex]1,2,3,6[/tex].
These are 4 outcomes out of total 10 outcomes.
The probability of selecting 4 or a factor of 6 is:
[tex]\displaystyle \frac{1}{10} +\frac{4}{10} =\frac{5}{10} =\frac{1}{2}[/tex]
Two friends are standing at opposite corners of a rectangular courtyard. The dimensions of the courtyard are 12 ft. by 25 ft. How far apart are the friends?
Answer:
27.73 feet
Step-by-step explanation:
Use the Pythagorean theorem. It easiest to think of the distance between the two friends as a triangle in the rectangle. One side is 12ft and the other is 25ft.
12^2+25ft^2=769
The square root of 769 is 27.73
Answer:
27.73 Ft
Step-by-step explanation:I took the test
Determine the point estimate of the population proportion and the margin of error for the following confidence interval.Lower boundequals0.212,upper boundequals0.758,nequals1200The point estimate of the population proportion is . 485.(Round to the nearest thousandth as needed.)The margin of error is 0.273.(Round to the nearest thousandth as needed.)
Answer: The point estimate of the population proportion is . 485.
The margin of error is 0.273.
Step-by-step explanation:
Confidence interval for population proportion(p):
sample proportion ± Margin of error
Given: Lower bound of confidence interval = 0.212
Upper bound = 0.758
⇒sample proportion - Margin of error=0.212 (i)
sample proportion + Margin of error= 0.758 (ii)
Adding (i) and (ii) , we get
2(sample proportion) =0.970
⇒ sample proportion = 0.970÷2= 0.485
Since sample proportion is the point estimate of the population proportion.
So, the point estimate of the population proportion= 0.485
Now put sample proportion =0.485 in (ii), we get
0.485+ Margin of error= 0.758
⇒ Margin of error= 0.758 - 0.485 =0.273
i.e. The margin of error is 0.273.
does x-2/x-6 simplify to 1/3 ?
explain why or why not
Answer:
no it is not 1/3
Step-by-step explanation:
(x-2) / (x-6)
This does not simplify
Rewriting x-2 as (x-6 +4)
(x-6 +4)/ ( x-6)
Replacing x-6 as m
( m+4) /m
Simplifying
m/m + 4/m
1 + 4/m
Replacing m with x-6
1 + 4/ ( x-6)
This is not 1/3
Please help . I’ll mark you as brainliest if correct!
Answer:
Stocks = $15,500
Bonds = $107,250
CD's = $47,250
Step-by-step explanation:
S + B + C = 170000
.0325S + .038B .067C = 7745
60,000 + C = b
S = $15,500
B = $107,250
C = $47,250
What value of x makes this equation true?
17 5 - 7 = -4
x=
y Su
What value of x makes this equation true? X/6-7=-4
Answer:
x=18
Step-by-step explanation:
x/6 - 7 = -4
x/6 = 3
(x/ 6) * 6 = 3*6
x = 18
These girts stasts jogging from the same point around
acircular track and they complete one round in 24
Seconds 36 seconds and 48 seconds respectively,
After.
how much time will they meet atone point?
Answer:
2hrs 24mins
Step-by-step explanation:
Very simple the time they will meet again at the point will be the LCM of their various time taken to complete a cycle.
Ans LCM(24, 36, 48) = 144 mins
= 2hrs 24mins
Answer:
The answer is 2 hours and 24 minutes
Step-by-step explanation:
Hope you get this right:)
The efficiency for a steel specimen immersed in a phosphating tank is the weight of the phosphate coating divided by the metal loss (both in mg/ft2). An article gave the accompanying data on tank temperature (x) and efficiency ratio (y).
Temp. 174 176 177 178 178 179 180 181
Ratio 0.86 1.31 1.42 1.01 1.15 1.02 1.00 1.74
Temp. 184 184 184 184 184 185 185 186
Ratio 1.43 1.70 1.57 2.13 2.25 0.76 1.37 0.94
Temp. 186 186 186 188 188 189 190 192
Ratio 1.85 2.02 2.64 1.53 2.48 2.90 1.79 3.16
(a) Determine the equation of the estimated regression line. (Round all numerical values to five decimal places.)
y =
(b) Calculate a point estimate for true average efficiency ratio when tank temperature is 186. (Round your answer to four decimal places.)
(c) Calculate the values of the residuals from the least squares line for the four observations for which temperature is 186. (Round your answers to four decimal places.)
(186, 0.94)
(186, 1.85)
(186, 2.02)
(186, 2.64)
(d) What proportion of the observed variation in efficiency ratio can be attributed to the simple linear regression relationship between the two variables? (Round your answer to four decimal places.)
Answer:
Kindly check explanation
Step-by-step explanation:
Given the data:
Temp. 174 176 177 178 178 179 180 181
Ratio 0.86 1.31 1.42 1.01 1.15 1.02 1.00 1.74
Temp. 184 184 184 184 184 185 185 186
Ratio 1.43 1.70 1.57 2.13 2.25 0.76 1.37 0.94
Temp. 186 186 186 188 188 189 190 192
Ratio 1.85 2.02 2.64 1.53 2.48 2.90 1.79 3.16
A)
Using the online linear regression calculator, the lie of best fit which models the data above is :
ŷ = 0.09386X - 15.55523
Where ;
X = independent variable
ŷ = predicted or dependent variable
- 15.55523 = intercept
0.09386 = gradient / slope
B)
Point estimate when tank temperature is 186
ŷ = 0.09386(186) - 15.55523
ŷ = 17.45796 - 15.55523
ŷ = 1.90273
C)
Residual error (y - ŷ), ŷ = 1.90273 when x = 186
(0.94 - 1.90273) = −0.96273
(1.85 - 1.90273) = −0.05273
(2.02 - 1.90273) = 0.11727
(2.64 - 1.90273) = 0.73727
D)
To determine the proportion of observed variation in efficiency ratio, we find the Coefficient of determination R^2, which can be found using the online Coefficient of determination calculator : the r^2 value obtained is 0.4433.
4. Create your own scenario for the variable expression below. Then, suggest values for the variables and solve. 14x + 12y
Answer:
Cost of pencil = $20
Cost of copy = $6
Step-by-step explanation:
Statement.
Gill buys 14 copy and 12 pencils and pays a total $324, if the value of 1 copy and 1 pencil is $26, find cost of copy and pencil.
Computation:
Assume.
Cost of copy = x
Cost of pencil = y
So,
x + y = 26.......Eq1
And
14x + 12y = 324.........Eq2
From Eq1 ad Eq2
Cost of pencil = $20
So,
Cost of copy = $6
Niall and Zayn buy 14 concert tickets for them and their friends to go see 5sos and 12 concert tickets for them and their friends to go see Little Mix with a total cost of $648. If the value of 1 5sos ticket and 1 Little Mix ticket is $52, and the Little Mix ticket is $4 more than the 5sos ticket, find cost of both tickets.
5sos = x
Little Mix = y
52 / 2 = 26
26 - 2 = 24
26 + 2 = 26
x = 24
y = 28
5sos tickets = $24 each
Little Mix tickets = $26 each
A survey showed that among 785 randomly selected subjects who completed four years of college, 144 of them are smokers and 84 do not smoke (based on data from the American Medical Association). Suppose you want to test at the 0.01 significance level the claim that the rate of smoking among those with four years of college is less than the 27% rate for the general population.
A. State the null and alternative hypotheses.
B. Find the sample statistic and the p-value.
C. What is your conclusion?
Answer:
We conclude that the rate of smoking among those with four years of college is less than the 27% rate for the general population.
Step-by-step explanation:
We are given that a survey showed that among 785 randomly selected subjects who completed four years of college, 144 of them are smokers.
Let p = population proportion of smokers among those with four years of college
So, Null Hypothesis, [tex]H_0[/tex] : p [tex]\geq[/tex] 27% {means that the rate of smoking among those with four years of college is more than or equal to the 27% rate for the general population}
Alternate Hypothesis, [tex]H_A[/tex] : p < 27% {means that the rate of smoking among those with four years of college is less than the 27% rate for the general population}
The test statistics that will be used here is One-sample z-test for proportions;
T.S. = [tex]\frac{\hat p-p}{\sqrt{\frac{p(1-p)}{n} } }[/tex] ~ N(0,1)
where, [tex]\hat p[/tex] = sample proportion of smokers = [tex]\frac{144}{785}[/tex] = 0.18
n = sample of subjects = 785
So, the test statistics = [tex]\frac{0.18-0.27}{\sqrt{\frac{0.27(1-0.27)}{785} } }[/tex]
= -5.68
The value of z-test statistics is -5.68.
Also, the P-value of the test statistics is given by;P-value = P(Z < -5.68) = Less than 0.0001
Now, at a 0.01 level of significance, the z table gives a critical value of -2.3262 for the left-tailed test.
Since the value of our test statistics is less than the critical value of z, so we have sufficient evidence to reject our null hypothesis as it will fall in the rejection region.
Therefore, we conclude that the rate of smoking among those with four years of college is less than the 27% rate for the general population.
PLEAS HELP...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?
*a clearer picture containing the graph is shown in the attachment
Answer:
20% of the class earned a D
Step-by-step Explanation:
Step 1: Determine the total number of students represented on the graph:
9 students => D
5 students => C
14 students => B
17 students => A
Total number of students = 45
Step 2: Express each category of students who scored a particular grade as a fraction and as percentage.
9 students => D => [tex] \frac{9}{45} = \frac{1}{5} [/tex] => as percentage, we have [tex] \frac{1}{5} * 100 = 20 percent [/tex]
5 students => C => [tex] \frac{5}{45} = \frac{1}{9} [/tex] => as percentage, we have [tex] \frac{1}{9} * 100 = 11.1 percent [/tex]
14 students => B => [tex] \frac{14}{45} [/tex] => as percentage, we have [tex] \frac{14}{45} * 100 = 31.1 percent [/tex]
17 students => A => [tex] \frac{17}{45} [/tex] => as percentage, we have [tex] \frac{17}{45} * 100 = 37.8 percent [/tex]
Step 3: Check each statement to see if they are true or not based on the calculations above.
Statement 1: "⅕ of the students earned a C."
This is NOT TRUE From our calculation, ⅑ of the students earned a C.
Statement 2: "3% more students earned an A than a B." This is also NOT TRUE.
37.8% earned A, while 31.1% earned a B. Thus, about 6.7% more students earned an A than a B.
Statement 3: "20% of the class earned a D". This is TRUE.
Check calculation in step 2.
Statement 4: "¼ of the class earned a B". This is NOT TRUE.
¼ is 25% of the class. Those who earned a B account for 31.1% not 25% (¼ of the class).
The correct statement is: "20% of the class earned a D"
