Question

Paras has a certain average for $12$ tests. In the ${13}^{\text{th}}$ test, he scores $80$ marks, thereby increasing his average by $6$ marks. What is his new average?

• A. $13$
• B. $8$
• C. $5$
• D. $10$

Answer 1

The correct option is B $8$

Let Paras's average be $x$ marks for $12$ tests.
Then, Paras scores $12x$ marks in $12$ tests.
In the ${13}^{\text{th}}$ test, he scores $80$ marks. Consequently, the average becomes $(x+6).$
So, $12x+80=13\times (x+6)$
$\Rightarrow 12x+80=13x+78$
$\Rightarrow x=2$
$\therefore$ New average $=x+6=8$ marks