A pupil's marks were wrongly entered as $83$ instead of $63.$ Due to that, the average marks for the class increased by its half. Find the original average marks.

60

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50

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40

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30

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Solution

The correct option is C $40$
wrongly entered $= 83$
Correct number $= 63$
Let the average marks $= x$
New avaerage marks $= (x + \frac{x}{2})$
Let the number of pupil be $y$
Total original marks $x y$
After mistaken $= (x + \frac{x}{2}) y$
So, $x y + 20 = (x + \frac{x}{2}) y$
$x y + 20 = x y + \frac{x y}{2}$
$x y = 40$ Ans

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A pupil's marks were wrongly entered as 83 instead of 63. Due to that, the average marks for the class increased by its half. Find the original average marks.

The correct option is C 40wrongly entered =83Correct number =63Let the average marks =xNew avaerage marks =(x+x2)Let the number of pupil be yTotal original marks xyAfter mistaken =(x+x2)ySo, xy+20=(x+x2)yxy+20=xy+xy2xy=40 Ans

A pupil's marks were wrongly entered as $83$ instead of $63.$ Due to that, the average marks for the class increased by its half. Find the original average marks.