Question

The mean marks of 20 student is 62 it was later discovered that one of the student marks were written wrongly as 86 instead of 68 find the correct mean

Answer 1

Given:

The mean marks of 20 student is 62 it was later discovered that one of the student marks were written wrongly as 86 instead of 68.

To find:

Correct mean.

Calculation:

Initial arithmetic mean :

$\rm{ \therefore \: \dfrac{x_{1} +x_{2} + ..... +x_{20} }{20} = 62}$

$\rm{ = > \: x_{1} +x_{2} + ..... +x_{20} = 62 \times 20}$

$\rm{ = > \: x_{1} +x_{2} + ..... +x_{20} = 1240}$

Now , term 68 was wrongly written as 86:

So, new total sum :

$\rm{ \therefore \: \sum(x_{new}) = x_{1} +x_{2} + ..... +x_{20} -86+68 }$

$\rm{ = > \: \sum(x_{new}) =1240 - 86 + 68 }$

$\rm{ = > \: \sum(x_{new}) =1222 }$

So, new mean :

$\rm{ = > new \: mean = \dfrac{ \sum(x_{new})}{20} }$

$\rm{ = > new \: mean = \dfrac{1222}{20} }$

$\rm{ = > new \: mean = 61 }$

So, correct mean is 61 marks.

Answer 2

Answer:

answer is 61.1...........................