Negative marking is a type of marking system where for every question you answer wrongly, you not only get no marks for that particular question but are also deducted extra marks from your previous total.
Let me explain it with an example:
Suppose in an exam, you have 5 question in total, each of one mark each. So the maximum marks that you can score is 5 marks. And suppose you do one question wrong, then you get 4 marks. That is according to a marking system which does not have negative marking.
However, suppose there is a negative marking of 2 marks for every wrong answer. Then instead of getting 4 marks, you will get only 2. This is because they will give you +4 marks for the four correct answers and then -2 for the wrong answer.
So +4+(-2) = 4-2 = 2. That's the mathematical explanation
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