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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 got increased by half (1/2). The number of pupils in the class is:

110
220
340
473

Answer:- 1

Explanation:-

Solution:

\begin{aligned} Let there be x pupils in the class . \\ Total increase in marks \\ = (x \times \frac{1}{2}) = \frac{x}{2} \\ ∴ \frac{x}{2} = (83 - 63) \\ \Rightarrow \frac{x}{2} = 20 \\ \Rightarrow x = 40 \end{aligned}

$\eqalign{ & {\text{Let}}\,{\text{there}}\,{\text{be}}\,x\,{\text{pupils}}\,{\text{in}}\,{\text{the}}\,{\text{class}}{\text{.}} \cr & {\text{Total}}\,{\text{increase}}\,{\text{in}}\,{\text{marks}} \cr & = \left( {x \times \frac{1}{2}} \right) = \frac{x}{2} \cr & \therefore \frac{x}{2} = \left( {83 - 63} \right) \cr & \Rightarrow \frac{x}{2} = 20 \cr & \Rightarrow x = 40 \cr}$

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", "dateCreated": "7/24/2019 10:09:12 AM", "author": { "@type": "Person", "name": "Nitin Sir" } }, "suggestedAnswer": { "@type": "Answer", "text": "

Solution:

\begin{aligned} Let there be x pupils in the class . \\ Total increase in marks \\ = (x \times \frac{1}{2}) = \frac{x}{2} \\ ∴ \frac{x}{2} = (83 - 63) \\ \Rightarrow \frac{x}{2} = 20 \\ \Rightarrow x = 40 \end{aligned}

$\eqalign{ & {\text{Let}}\,{\text{there}}\,{\text{be}}\,x\,{\text{pupils}}\,{\text{in}}\,{\text{the}}\,{\text{class}}{\text{.}} \cr & {\text{Total}}\,{\text{increase}}\,{\text{in}}\,{\text{marks}} \cr & = \left( {x \times \frac{1}{2}} \right) = \frac{x}{2} \cr & \therefore \frac{x}{2} = \left( {83 - 63} \right) \cr & \Rightarrow \frac{x}{2} = 20 \cr & \Rightarrow x = 40 \cr}$ ", "dateCreated": "7/24/2019 10:09:12 AM" } }

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