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#### Sudharaka

##### Well-known member
MHB Math Helper

If the mean average for 24 students is 78% and another student got 67% what is the mean average for the 25 students?

#### Sudharaka

##### Well-known member
MHB Math Helper

If the mean average for 24 students is 78% and another student got 67% what is the mean average for the 25 students?
Hi Kizzy,

Let $$x_{i}$$ be the marks of the $$i^{th}$$ student. Then the mean value of marks for 24 students is,

$M_{24}=\frac{1}{24}\sum^{24}_{i=1} x_{i}=78$

$\Rightarrow \sum^{24}_{i=1} x_{i}=78\times 24~~~~~~~~~~(1)$

Since the 25th student got 67% marks,

$M_{25}=\frac{1}{25}\left(67+\sum^{24}_{i=1} x_{i}\right)~~~~~~~~(2)$

Using (1) and (2) you'll be able to calculate $$M_{25}$$.