F1 Maths (己解答)

丸媽媽

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There are 18 True-or-False questions in Mathematics test. 2 marks will be given for each correct answer and 1 mark will be deducted for each wrong answer. If Mimi answers all the questions and gets 24 marks, how many correct answers has she got? (Ans. 14)

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[ 本帖最後由 丸媽媽 於 09-11-13 01:02 編輯 ]

happy-fish

There are 18 true-or-False questions in a Mathematics test.2 marks will be given for each correct answer and 1 mark will be deducted for each wrong answer.If Mimi answers all the questions and gets 24 marks,how many correct answers has she got?

Let she has got correct answers be x.

P.S.要用方程式!!!





Let she got x correct answers.

Then, she got 18-x wrong answer.



2x + (18-x)(-1) = 24

2x -18 +x = 24

3x -18 = 24

3x = 24 + 18

3x = 42

x = 14



Ans: She got 14 correct answer.



Checking:

2*14+(18-14)(-1)

=28+(-4)

=24

Pls refer to the following :-
http://hk.knowledge.yahoo.com/question/question?qid=7006112501279

丸媽媽

happy-fish,

Thanks so much