A pupils marks were wrongly entered as 83 instead of 63. Due to that the average marks for the class got increased by half (1/2). The number of pupils in the class is:
10
20
40
73
Explanation:
Let there be $ x $ pupils in the class.
| Total increase in marks =$ \left(x \times\dfrac{1}{2} \right) $=$ \dfrac{x}{2} $ |
| $\therefore \dfrac{x}{2} $= (83 - 63) $\Rightarrow \dfrac{x}{2} $= 20 $\Rightarrow$ $ x $= 40. |