The average weight of $20$ students was calculated $70$ kg. It was later discovered that one weight was misread as $70$ instead of $90$ , the correct average in kg is

80

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72

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75

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71

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Solution

The correct option is D $71$
Wrong average $= 70 ∴$ Wrong sum of weight of $20$ students $= 20 \times 70$
$∴$ Correct sum of weights of $20$ students
$= 1400 -$ wrong weight $+$ correct weight
$= 1400 - 70 + 90 = 1420$
$∴$ Correct mean $= \frac{1420}{20} = 71$ kg.

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The average weight of 20 students was calculated 70 kg. It was later discovered that one weight was misread as 70 instead of 90, the correct average in kg is

The correct option is D 71Wrong average =70∴ Wrong sum of weight of 20 students =20×70∴ Correct sum of weights of 20 students =1400−wrong weight+correct weight =1400−70+90=1420∴ Correct mean =142020=71 kg.

The average weight of $20$ students was calculated $70$ kg. It was later discovered that one weight was misread as $70$ instead of $90$ , the correct average in kg is

The correct option is D $71$
Wrong average $= 70 ∴$ Wrong sum of weight of $20$ students $= 20 \times 70$
$∴$ Correct sum of weights of $20$ students
$= 1400 -$ wrong weight $+$ correct weight
$= 1400 - 70 + 90 = 1420$
$∴$ Correct mean $= \frac{1420}{20} = 71$ kg.