Question

In a examination, a student attempted 15 questions correctly and secured 40 marks. If there were two types of questions i.e. of 2 marks and 4 marks, how many questions of 2 marks did he attempt correctly ?

• A. $5$
• B. $10$
• C. $12$
• D. $15$

Answer 1

The correct option is B $10$

Let the 2 marks questions attempted correctly $=x$
The 4 marks questions attempted correctly $=y$
Now,
$x+y=15$ -----------(I)
$2x+4y=40$ ----------(II)
Multiply equation I by 4 and subtract from II
$2x+4y-4x-4y=40-60$
$-2x=-20$
$x=10$
Number of 2 marks questions attempted correctly $=10$
Hence, option 'B' is correct.