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Question 570946: I took a practice test and got 20 WRONG out of 50 QUESTIONS so what would my grade be? Please explain how you got to your answer.
Answer by jim_thompson5910(21667)

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If there are 50 questions, and you got 20 wrong, then you got 50-20 = 30 correct.

So the grade as a percentage is (30/50)*100 = 0.6*100 = 60%

Question 570894: 700 points will get 100% how many points will get 80%
Answer by jim_thompson5910(21667)

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700*0.8 = 560

So 560 points will get you 80%

Question 570888: a person took four tests and got an 88, 86, 84, an a 93. the last test is worth 3 test grades. what do u have to get on the last test to get a 90 for the class?
Answer by stanbon(48516)

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a person took four tests and got an 88, 86, 84, an a 93. the last test is worth 3 test grades. what do u have to get on the last test to get a 90 for the class?
------
Equation:
(88+86+93+3x)/6 = 90
--------------
267+3x = 540
3x = 273
x = 91
----------------
Cheers,
Stan H.

Question 570837: If i got 77% on my first test what percentage should i get on my last test to get a 90% average?
Answer by Alan3354(21555)

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If i got 77% on my first test what percentage should i get on my last test to get a 90% average?
---------------
If you have only those 2 tests, you need 103%
----
(77 + score)/2 = 90

Question 570657: hello?

Answer by Alan3354(21555)

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hi

Question 570259: WHAT IS 82% OF 450
Found 2 solutions by JBarnum, Maths68:
Answer by JBarnum(1826)   (Show Source):
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um im pretty sure he said 82% not 80%...
.82(450)=369

Answer by Maths68(1140)   (Show Source):
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=
=
=
=
=
=

Question 570267: what is the average of 1/4 and 1/6?
Answer by Maths68(1140)   (Show Source):
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=
=
=
=
=

Question 570171: What is the average (arithmetic mean) mean of 213 and 215 ?

Answer by stanbon(48516)   (Show Source):
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What is the average (arithmetic mean) mean of 213 and 215 ?
----
Add the 2 numbers and divide the sum by 2.
Ans: 214
--------------
Cheers,
Stan H.

Question 569905: natasha got 5 different grades on her math tests. Both the mean and median of her scores was 80. What are five scores she could have gotten on the tests?
Answer by ankor@dixie-net.com(12684)   (Show Source):
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natasha got 5 different grades on her math tests.
Both the mean and median of her scores was 80.
What are five scores she could have gotten on the tests?
:
We know the median test = 80
:
How about 60, 70, 80, 90, 100?

Question 569329: im currently getting 97% in my math class, so would the minimum percent i need to get on my next test to keep my mark at 97%, be 97%? if not, then what would the minimum percent needed to keep it at 97%?
Answer by richard1234(4789)   (Show Source):
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It would be 97%.

Question 569356: Ok, my son is has a problem in Algebra, he is in the 9th grade. I can get the answer for him but he need to write it in algebra terms. I never took algebra in school, so if I can tell you the question. can you please tell me how to write it in algebra terms.
Mike just got a phone bill for $27.60. he is charge $.07 per minute for local calls and $.20 for long distance calls. he talked for a total of 320 minutes. How many long distance minutes did he use?
It sounds just like a typical story problem and easy to solve but feel bad that I can't put it in Algebra form
Thanks so much,
Until Next time,
Sue
Answer by ankor@dixie-net.com(12684)   (Show Source):
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Mike just got a phone bill for $27.60. he is charged $.07 per minute for local calls and $.20 for long distance calls. he talked for a total of 320 minutes.
How many long distance minutes did he use?
:
We need two equation to solve two unknowns, we are going to use substitution to solve this
Let x = no. of local minutes
Let y = no. of L.D minutes
;
x + y = 320; (total minutes equation
x = (320-y); this form for substitution
:
.07x + .20y = 27.60; (total cost equation)
Replace x with (320-y)
.07(320-y) + .20y = 27.60
22.4 - .07y + .20y = 27.60; (multiplied what's inside the brackets)
-.07y +.20y = 27.60 - 22.4
.13y = 5.20
y =
y = 40 minutes of L.D calls which is answer they want
:
then in order to check our solution
using x + y = 320
x + 40 = 320
x = 320 - 40
x = 280 minutes of Local calls
:
:
Confirm this in the equation; .07x + .20y = 27.60
.07(280) + .20(40) =
19.60 + 8.00 = 27.60;

Question 569108: The Radioactive isotope technetium 99m (99mTc) is used in imaging the brain. the isotope has a half life of 6 hours. If 12 milligrams are used how much will be present after three hours and 24 hours?
Answer by htmentor(580)   (Show Source):
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The Radioactive isotope technetium 99m (99mTc) is used in imaging the brain. the isotope has a half life of 6 hours. If 12 milligrams are used how much will be present after three hours and 24 hours?
===================
The radioactive decay formula can be written
where T = the half-life, N0 = the amount at t=0, and N(t) = the amount at time t
Given: N0 = 12 mg, T = 6 h
So the formula can be written
The amount after 3 hrs is mg
The amount after 24 hrs is mg

Question 569105: The earliest mechanical clock appeared around 1350 in europe and would gain or lose and average of 30 minutes per day. After that, accuracy roughly doubled every 30 years. find the predicted accuracy of the clock in the years 1700 and 2000.
Found 2 solutions by josmiceli, Alan3354:
Answer by josmiceli(6778)   (Show Source):
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If is the time gained or lost the 1st year,
After 30 yrs:

Next 30 yrs:

Next 30 yrs:

----------
So, at the end of yrs,
The accuracy is
If

min/day
min/day
You can use log to solve this. Call it
for accuracy

When you find , then

( I don't have calculator handy )

Answer by Alan3354(21555)   (Show Source):
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The earliest mechanical clock appeared around 1350 in europe and would gain or lose and average of 30 minutes per day. After that, accuracy roughly doubled every 30 years. find the predicted accuracy of the clock in the years 1700 and 2000.
----------------
"accuracy...doubled..." is not a good term. If the accuracy is 10%, then double that is 20% ??
----
If you mean the error was reduced by a factor of 2:
1350 - 1700 = 350 yrs
350/30 =~ 12 periods
30 mins error * (1/2)^12 = 30/1024 =~ 0.03 min/day = 1.8 seconds/day
------------
1350 - 2000 = 650 yrs = 22.7 periods
30 min*(1/2)^22.7 =~ 4.403E-6 min/day
=~ 264 microseconds/day

Question 568769: what grade would i have if i got 15% wrong on my test in math
Answer by Alan3354(21555)   (Show Source):
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what grade would i have if i got 15% wrong on my test in math
-----------
It depends on what grade 85% is.
It varies with classes and teachers.

Question 568644: In the mathematical statement "90 is 25% of 360," the percentage is:
A) 90
B) 25%
C) 360
D) None of the above.
Answer by nyc_function(2626)   (Show Source):
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The word [is] is often used in math to represent the equal sign.

90 = 0.25 x 360

The percentage in the statement is 25%.

To multiply a percent, remove the percent symbol and convert the value to decimal form.
So, 25% becomes 0.25, you see?

NOTE: 0.25 x 360 = 90

90 = 90

Question 567596: a teacher gave five test in english gina got the following score in the fist four tests. 83,86,79, and 80 what must be her score in the fifth test so that he aveege is 85%
Answer by bucky(2097)   (Show Source):
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Let's try two different ways to solve this problem.
.
First, let's look at how many points Gina must score on 5 tests to have an average score of 85. The average score of 85 will come from dividing the total number of points scored by 5 which is the number of tests. Ask yourself, "What number divided by 5 gives an answer of 85?" The answer to that question is 425, and you can prove that by dividing 5 into 425 to see that the answer is truly 85.
.
You can think about this in several ways. If Gina were to score 85 on every one of the 5 tests she would score 5 times 85 = 425 points and because she scored 85 on every test, her average score would be 85. That tells you that 425 points is the total that Gina needs to score on the five tests. You could also set up an equation that says the unknown number of total points needed is X and when you divide by the total number of tests (5) the answer needs to be 85. This equation would be:
.

.
and you would multiply both sides by 5 to get rid of the denominator on the left side. This multiplication would result in:
.

.
on the left side the 5 in the numerator cancels with the 5 in the denominator and the left side of the equation becomes just X. On the right side of the equation multiply 5 times 85 and you get 425.
.
So now we know that Gina must score a total of 425 points on the 5 tests. The problem tells you that on the first 4 tests her scores were 83, 86, 79, and 80. Add these 4 scores together and you get 328. You know that she needs a total of 425 points on 5 tests, so all the remaining points must be scored on the fifth test. Subtract the 328 points that she currently has from the 425 points she needs, and you find that the points she needs on the fifth test are 97. That's the answer. Gina needs a grade of 97 on the fifth test in order to average 85 on the 5 tests.
.
There's another way you can solve this problem. Remember that we said if Gina scored 85 on every test she would have an average score of 85 for all 5 tests? Well, let's use that fact to solve the problem. On the first test she scored 83 points. That's 2 points below what she would need to get 85. Let's indicate this by -2. On the second test she scored 86 points. That's 1 point above what she would need to get 85. Let's indicate this by +1. On the third test she scored 79 which is 6 points below 85. Call this -6. And on the fourth test she scored 80 which is -5 points below 85. Add up these 4 plus and minus scores as follows:
.

.
So going into the fifth test Gina is 12 points below what she needs to get. But we assumed she would get an 85 on the last test (just as she needed to do on all 5 tests). So on the last test she needs to score 85 plus 12 extra points to make up for her lower grades on the first 4 tests, and this is a total of 97 points, just as we found by the first method.
.
In summary, the answer to the question is that Gina needs to score 97 points on the last test.
.
I hope this helps you to understand the problem a little better and you can understand several ways that it (or other problems like it) can be solved.
.

Question 567342: what is the answer to 7 divided by 7/5

Answer by Edwin McCravy(6932)   (Show Source):
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7 ÷ Put 7 over 1 to make it a fraction too: ÷ Invert the second fraction and change the ÷ to × × Cancel the 7's × Erase the 1 on the bottom: Answer: 5 Edwin

Question 567277: the average of 3 numbers is 63. What is the value of a fourth number x if the average of the four numbers is 60?
Answer by htmentor(580)   (Show Source):
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the average of 3 numbers is 63. What is the value of a fourth number x if the average of the four numbers is 60?
====================
Let S = the sum of the 3 numbers
Then the average of the 3 numbers = 63 = S/3 -> S = 189
When the fourth number, x, is added the average = (S+x)/4 = 60
189+x = 240
x = 51

Question 567193: find the average of 7, 11, 14, 28, and 71
Answer by stanbon(48516)   (Show Source):
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Add those numbers and divide the sum by 5 to get the average.
Cheers,
Stan H.

Question 566844: what is the mean of 80+83+79+86
Answer by solver91311(12118)   (Show Source):
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The mean is the sum of the data divided by the number of data points. The problem is the way that you represented your data. You wrote 80+83+79+86 which is really only one number. So if you really meant "What is the mean of 80, 83, 79, and 86, then sum the 4 numbers and divide by 4. But if you meant exactly what you wrote, only divide by 1.

John

My calculator said it, I believe it, that settles it

Question 566780: what is the average of 86, 79, 81, 69, 80
Answer by jim_thompson5910(21667)   (Show Source):
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Average = (Sum of the values)/(Number of values)

Average = (86+79+81+69+80)/5

Average = 395/5

Average = 79

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Jim
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Question 566511: a coffee can is shaped like a cylinder 13cm high.Its base is a circle with diameter of 10 cm. What is the circumference of the base?
Answer by bucky(2097)   (Show Source):
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The fact that the coffee can is 13 cm high is just extra information. You can ignore that because it has nothing to do with finding the circumference of the base.
.
The circumference of a circle is found by using one of two formulas. You can use either this first equation:
.

.
in which C is the circumference, r is the radius, and is the Greek letter pi which is a number with a never ending number of decimal places. The value of pi rounded off to 9 decimal places is 3.141592654
.
Or you can use this second equation:
.

.
in which C again is the circumference, d is the diameter, and again pi rounded to 9 decimal places is 3.141592654.
.
Since you were given the diameter of the circular base, you can use the second equation directly as follows:
.

.
and since d is given as 10 cm, you can substitute 10 for d to get:
.

.
This is the answer. However, normally we would reverse the two factors on the right side, so we would write the answer as:
.

.
And don't forget that since the units of the diameter is cm, the units for the circumference is also cm.
.
If your book or teacher wants you to give your answer in terms of a number, you can substitute 3.141592654 for , and when you multiply that by 10 you get the answer for C as:
.
cm
.
So you can say that C is approximately 31.416 cm. which should be more than accurate enough to express the circumference of a coffee can.
.
Hope this helps you to understand the problem a little better.
.

Question 566416: A stuent received scores of 51, 79, and 57 on their first three tests for a class. There will be a total of four tests for the class and the student hopes to acheive and average score of n in the class. Express the score, S, needed on the fourth test to acheive this average, as a function of n.
Answer by ankor@dixie-net.com(12684)   (Show Source):
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A stuent received scores of 51, 79, and 57 on their first three tests for a class.
There will be a total of four tests for the class and the student hopes to acheive and average score of n in the class.
Express the score, S, needed on the fourth test to acheive this average, as a function of n.
:
= n
s + 187 = 4n
s = 4n - 187

Question 566313: If I have 73% in a class and I get a 63% on a test and the test weighs 30% what will my grade be
Answer by ad_alta(170)   (Show Source):
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Your grade will be (0.70)(73)+(0.30)(63)=70.

Question 565819: a student earned a grade of 80% on a math test that had 20 problems . How many did he get right?
Answer by ad_alta(170)   (Show Source):
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He got (0.80)(20)=16 right.

Question 565875: If I have a 84.23% in English class, and I get 93% on my finals which is 20% of my grade, what will my final score be?
Answer by ad_alta(170)   (Show Source):
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Your grade will be (0.8)84.23+(0.2)(93)=85.98.

Question 565627: The average SAT score of eleven students was 2,ooo. When Mary's score was added to the other eleven scores, the average went up to 2,010. What is the positive difference between her score and the initial average score?
Answer by ad_alta(170)   (Show Source):
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Let 'M' be Mary's score. Then (2000*11+M)/(12)=2010. Thus M=2120. The difference is 120.

Question 565516: A student scored 65,86,and 98 on three algebra test. What must he score on the fourth test in order to have an average grade of at least 85?
Answer by scott8148(5879)   (Show Source):
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65 + 86 + 98 + x = 4 * 85

Question 565071: If $5000 is invested at an annual interest rate of 9% compounded continuously, how much is available after 5 years? Round to the nearest whole dollar. (Points: 1)
Answer by nyc_function(2626)   (Show Source):
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The following link will show you how to solve this question.
If after visiting the link you are not clear about what to do, get back to me.
http://www.mathwarehouse.com/compound-interest/continuously-compounded-interest.php

Question 565040: Suppose 88 people took the final exam in a math class. If 11 people got an A on the final exam, what fraction of the students did not get an A on the exam? Write your answer in lowest terms.
Answer by stanbon(48516)   (Show Source):
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Suppose 88 people took the final exam in a math class. If 11 people got an A on the final exam, what fraction of the students did not get an A on the exam? Write your answer in lowest terms.
----
# not getting A's: 77
----
% not getting A's = 77/88 = 0.8750 = 87.5%
=====================================
Cheers,
Stan H.
===========

Question 564037: In the beginning of the second quarter i got a 78%. I failed 2 quizzes with a 42 & 64. And tests counts as 40% of my grade. then forgot to do 2 homework sheets which is 10% of my grade also. what is my grade so far?
Answer by richard1234(4789)   (Show Source):
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I don't know, but 99.9% chance that it is lower than a 78%. If this is your actual situation then you should study.

Question 563895: Hi there, i am trying to find my average for a module at university.

i have two units for the module:
one worth 60% where i got a C12
and the other worth 40% where i got an A18

the marking scale is as follows:
D (9-11) C (12-14) B (15-17) A (18-20)

Answer by Theo(2967)   (Show Source):
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if i understand this correctly, you got a 12 and an 18.
since the 12 is worth 60% and the 18 is worth 40%, then your weighted score would be 60% * 12 + 40% * 18 = 14.4 which would put you in the C14 category if they categorize you to the nearest integer.
it appears they are scoring from 0 to 20 where 0 = 0 and 20 = 100%
this means that the ratio of score units to grade percentage points is equal to 5.
this means that if you score a 12, then your grade percentage for the test was 12 * 5 = 60, and if you score an 18, then your grade percentage for the test was 18 * 5 = 90.
60% * 60 and 40% * 90 equals an overall grade percentage of 72.
based on the ratio, an overall grade percentage of 72 results in a score of 14.4 units because 72/5 = 14.4.
that's what i think anyway.
your overall score would be 14.4 which puts you closer to C14 than to B15 which would round you into the C14 category.
that's what i think anyway.

Question 563822: What is the average (arithmetic mean) of 4x + 5, 7x-6,and -8x+2
Answer by fcabanski(385)   (Show Source):
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AVG = sum/#numbers.

There are 3 values/numbers.

AVG = (4x+5+7x-6-8x+2)/3 = (3x+1)/3

If you need help understanding math so you can solve these problems yourself, then one on one online tutoring is the answer ($30/hr). If you need faster solutions with guaranteed detailed answers, then go with personal problem solving ($3.50-$5.50 per problem). Contact me at fcabanski@hotmail.com

Question 563704: My term mark prior to my final exam is 68%
My final exam is worth 20%.
Is there a way i can get a final mark of 80% ?
Answer by solver91311(12118)   (Show Source):
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Not if the maximum score on the final is 100%.

John

My calculator said it, I believe it, that settles it

Question 563558: the sum of the squares of three consecutive odd number is 83,find the number
Found 2 solutions by Alan3354, richard1234:
Answer by Alan3354(21555)   (Show Source):
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the sum of the squares of three consecutive odd number is 83,find the number
---------
83/3 =~ 27
sqrt(27) =~ 5, the middle number
--> 3, 5 & 7, plus and minus
------------
You can do
(x-2)^2 + x^2 + (x+2)^2 = 83, where x is the middle number
same answer

Answer by richard1234(4789)   (Show Source):
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3^2 + 5^2 + 7^2 = 83, (-7)^2 + (-5)^2 + (-3)^2

You could do it the algebraic way, but we know they're integers so guess-and-check is much faster.

Question 563232: If I have a 57% in my class and it counts for 80% of my grade, what's the lowest grade I can get on my final exam ( worth 20%) in order to pass my class?'
For example: do I have to get a 50% on the final exam to pass my class? or do I need to get 40% to pass etc...
Answer by stanbon(48516)   (Show Source):
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If I have a 57% in my class and it counts for 80% of my grade, what's the lowest grade I can get on my final exam ( worth 20%) in order to pass my class?'
---
You have 0.57*80 = 45.6 points
---------
If you need 70% to pass
you need (70-45.6) = 24.4 more points.
But only 20 points are available.
You cannot get the 70% you need.
=====================================
Cheers,
Stan H.
===============

Question 563221: If I have a 57% in my class and it counts for 80% of my grade, what's the lowest grade I can get on my final exam ( worth 20%) in order to pass my class?
Answer by Alan3354(21555)   (Show Source):
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If I have a 57% in my class and it counts for 80% of my grade, what's the lowest grade I can get on my final exam ( worth 20%) in order to pass my class?
------------
What is needed to pass?
--------
To make 50% overall,
57*80 + score*20 = 50*100
score = (5000 - 4560)/20
score = 22% needed on the final

Question 563197: The average of your first 7 quizzes was an 82. What do you need on your next quiz to raise your average to an 84?
Found 2 solutions by stanbon, Alan3354:
Answer by stanbon(48516)   (Show Source):
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The average of your first 7 quizzes was an 82. What do you need on your next quiz to raise your average to an 84?
--------------------------------
Total points from the 7 quizzes: 7*82 = 574
---
Total needed for the 8 quizzes: 8*84 = 672
----
Score needed on 8th quiz: 672-574 = 98
===========================================
Cheers,
Stan H.
===============

Answer by Alan3354(21555)   (Show Source):
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The average of your first 7 quizzes was an 82. What do you need on your next quiz to raise your average to an 84?
--------
An 84 avg for 8 quizzes = 8*84 = 672 points
7*82 = 574 points
672 - 574 = 98 points needed

Question 562712: everything in the store is 20% of for one day. if computers normally costs 399.99,what is the sale price, rounded to the nearest cent?
Answer by rfer(10417)   (Show Source):
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399.99*0.80=$319.99

Question 562562: if my class mark is 59% what do i need to make on an exam woth 30% to receive a passing mark
Found 2 solutions by ankor@dixie-net.com, solver91311:
Answer by ankor@dixie-net.com(12684)   (Show Source):
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if my class mark is 59% what do i need to make on an exam worth 30% to receive a passing mark
:
x = grade to make a 70 for class
:
= 70
413 + 3x = 700
3x = 700 - 413
3x = 287
x = 287/3
x ~ 96% will give you a passing mark

Answer by solver91311(12118)   (Show Source):
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Depends. How much do you have to get to pass?

Let represent the mark required to pass. Let represent the grade on the final exam.

A little algebra music, Maestro:

Plug in the appropriate value for and do the arithmetic. Hope that , or whatever the maximum possible score on the final turns out to be. For example, if a passing grade is a 75%, put a fork in yourself -- you are done.

John

My calculator said it, I believe it, that settles it