Average marks of 40 students in an English exam is 72 . Later it is found that three marks 64 , 62 a

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4.Average

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The average marks of $40$ students in an English exam is $72 .$ Later it is found that three marks $64 , 62$ and $84$ were wrongly entered as $68,65$ and $73.$ The average after mistakes were rectified is

A

$70$

B

$72$

C

$71.9$

D

$72.1$

Solution

Difference $=(64+62+84)-(68+65+73)$ $=210-206=4$

$\therefore \quad$ Correct average $=72+\frac{4}{40}=72.1$

Standard 13

Quantitative Aptitude

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