SOLUTION: A mathematical test consists of 20 problems .at the beginning everyone started with 20 points. for the correct answer, everyone gets 1 point for incorrect or missed question 1 poin

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Question 1136081: A mathematical test consists of 20 problems .at the beginning everyone started with 20 points. for the correct answer, everyone gets 1 point for incorrect or missed question 1 point is subtracted.mary final result is 24 how many correct answers did marry give
Found 2 solutions by ikleyn, greenestamps:
Answer by ikleyn(52858)   (Show Source): You can put this solution on YOUR website!
.
Let x be the number of correct answers.


Then the number of incorrect or missed is (20-x).


The balance equation is


    20 + x - (20-x) = 24.


Simplify and solve for x:


    20 + x - 20 + x = 24

    2x = 24               ===============>        x = 24/2 = 12.


ANSWER.  12 correct answers.


CHECK.  12 scores obtained and 8 scores lost.  20 + 12 - 8 = 24.   ! Correct !

Solved.


Answer by greenestamps(13203)   (Show Source): You can put this solution on YOUR website!


You can solve this by logical reasoning, although algebra can also be used.

Suppose Mary answers the first 4 questions right; then her score is 24 -- the score she ends up with.

For her final score to again be 24, the remaining 16 questions must be half right and half wrong -- i.e., 8 right and 8 wrong.

So overall she got 12 answers right and 8 wrong.
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