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 Elementary Math Fractions, Percentages, Word Problems, Equations, Inequations, Factorization, Expansion

 June 3rd, 2019, 04:19 PM #1 Senior Member   Joined: Jan 2012 Posts: 745 Thanks: 7 How many correct answers did she get? In a mathematics quiz, each correct answer gets 2 marks and a wrong answer attracts -1. Kevwe got a total of 19 in a quiz with 20 questions. How many correct answers did she get? I don’t seem to understand the problem. If she has 19marks and 2 marks is for each correct answer, I will say that she got 9 questions correct which fetched her (9 x 2) marks = 18 marks. I don’t know how the other 1 mark came about that made it 19 marks. By asking how many correct answers she got, I understand it to mean how many questions she answered correctly that gave 19 marks total. Is my understanding correct? if not I need better understanding to this problem. June 3rd, 2019, 04:28 PM #2 Senior Member   Joined: Sep 2015 From: USA Posts: 2,549 Thanks: 1399 basically we're talking about two equations There are 20 total questions, Kevwe gets every question either right or wrong. $r+w=20$ Right answers are +2 points, wrong answers are -1 points. Kevwe scored 19. $2r-w=19$ It's easy enough to solve this, add the two equations. $3r = 39$ $r=13$ $w=20-r = 7$ Kevwe got 13 questions correct, and 7 incorrect. Thanks from Chikis and topsquark June 4th, 2019, 01:48 AM   #3
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Thanks for the explanation and equation so far. I just want to ask some few questions:
Quote:
 Originally Posted by romsek wrong answers are -1 points.
Does this mean that for every question she answers wrongly, 1 mark will be subtracted from the scores she already have?

Apart from using equation, are there other ways this can be solved? June 4th, 2019, 02:41 AM #4 Global Moderator   Joined: Dec 2006 Posts: 20,966 Thanks: 2216 Had all 20 questions been answered wrongly, the total marks would have been -20. For each question answered correctly, 2 marks are awarded and one negative mark isn't awarded, making a total improvement of 3 marks. As she got a total of 19 marks, and 19 - (-20) = 39, she got 39/3 = 13 questions correct. Thanks from Chikis June 4th, 2019, 05:49 AM   #5
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Quote:
 Originally Posted by skipjack Had all 20 questions been answered wrongly, the total marks would have been -20.
What about when all the questions are answered correctly? Would it be 20 × (+2) i.e. 40 marks?

Quote:
 For each question answered correctly, 2 marks are awarded and one negative mark isn't awarded, making a total improvement of 3 marks. As she got a total of 19 marks, and 19 - (-20) = 39, she got 39/3 = 13 questions correct.
How? If she got 13 questions correct, is it not +2 × 13 = 36 marks, which is contrary to the 19 marks?

Last edited by skipjack; June 4th, 2019 at 01:15 PM. June 4th, 2019, 09:26 AM   #6
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Quote:
 Originally Posted by Chikis What about when all the questions are answered correctly? Would it be 20 × (+2) i.e. 40 marks? How? If she got 13 questions correct, is it not +2 × 13 = 36 marks, which is contrary to the 19 marks?
13 correct, 7 incorrect

13×2 - 7 = 26 - 7 = 19

2 × 13 = 26, not 36

Last edited by skipjack; June 4th, 2019 at 01:16 PM. June 4th, 2019, 10:21 AM #7 Senior Member   Joined: Jan 2012 Posts: 745 Thanks: 7 Suppose she had all the 20 questions correct what would be her score? June 4th, 2019, 11:47 AM   #8
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Quote:
 Originally Posted by Chikis Suppose she had all the 20 questions correct what would be her score?
Are you fooling around? Or you can't multiply 20 times 2 ? June 4th, 2019, 01:22 PM   #9
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Quote:
 Originally Posted by Chikis What about when all the questions are answered correctly? Would it be 20 × (+2) i.e. 40 marks?
Yes. Each wrong answer would reduce that total by 2 + 1 = 3,
so the number of wrong answers was (40 - 19)/3 = 7,
which means the number of correct answers was 20 - 7 = 13. Tags answers, correct Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Threads Thread Thread Starter Forum Replies Last Post EvanJ Probability and Statistics 28 October 5th, 2016 05:29 AM Lilian Probability and Statistics 2 June 6th, 2014 02:27 PM r-soy Algebra 6 March 5th, 2010 07:23 AM golfman44 Calculus 3 October 23rd, 2009 08:13 AM restin84 Calculus 2 September 11th, 2009 09:12 AM

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