Mehul had a Social Studies exam which was worth 20 marks.There were 10 questions worth 2 marks each.But there was negative marking scheme such that if Mehul gets a question correct then he will get 2 marks , but if he gets it wrong , he will get -0.5 marks.If Mehul scored 75% in the test and he attempted all the questions, Find the number of questions he got correct.
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Let the number of questions Mehul got correct be ' x ' and since the total questions are 1 0 , the ones he got wrong will be ( 1 0 − x ) .
Hence , the marks he got due to correct attempt = 2 ( x )
Hence , the marks he got due to wrong attempt = − 0 . 5 ( 1 0 − x )
Since he got 7 5 % , we can write equation:
2 x − 0 . 5 ( 1 0 − x ) = 1 0 0 7 5 × 2 0 2 x − 5 + 0 . 5 x = 1 5 2 . 5 x = 2 0 2 5 x = 2 0 0 x = 2 5 2 0 0 x = 8
Hence , Mehul got 8 questions correct. Cheers!