A pupil`s marks were wrongly entered as 83 instead of 63. Due to the average marks for the class got increased by half. 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 = (x $\times$ 1/2) = x/2
x/2 = (83 - 63) $\Rightarrow$ x/2 = 20 $\Rightarrow$ x = 40.
Let there be x pupils in the class.
Total increase in marks = (x $\times$ 1/2) = x/2
x/2 = (83 - 63) $\Rightarrow$ x/2 = 20 $\Rightarrow$ x = 40.