Question

If the mean of 5,7,8,a is 7 then a=

Answer 1

Heya
Here is your answer !!

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Mean of a given set of observations =
Sum of the observations / no. of observations

So , in this question ,
Mean = 7
Observations = 5 , 7 , 8 , a .
No. of observations = 4 .

So ,
7 = ( 5 + 7 + 8 + a ) / 4
=> 28 = 5 + 7 + 8 + a
=> 28 = 20 + a
=> 8 = a . [ Answer ] .

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Hope it helps !!