There are 180 multiple choice questions in a test.
Question:

There are 180 multiple choice questions in a test. If a candidate gets 4 marks for every correct answer and for every unattempted or wrongly answered question one mark is deducted from the total score of correct answers. If a candidate scored 450 marks in the test, how many questions did he answer correctly?

Solution:

Let the number of correctly answered questions be $x$.

Therefore, the number of unattempted or wrongly answered questions will be $(180-\mathrm{x})$.

According to the question,

$4 \mathrm{x}-1(180-\mathrm{x})=450$

or $5 \mathrm{x}=450+180$

or $\mathrm{x}=\frac{630}{5}=126$

Thus, number of correctly answered questions $=126$.

Number of unattempted or wrongly answered questions $=180-126=54$.