1.

The average mark scored by 50 students in a class were calculated to be 38.later it found ,that marks of two students were wrongly copied as 34&23 instead of 43 and 32. Find correct average marks

Answer»

Gien that, Average marks of 50 STUDENTS = 38.

Now,

Mean = (Sum of all observations)/(Total NUMBER of observations)

Let us assume that the sum of all observations is M.

So,

⇒ 38 = M/50

⇒ M = 50(38)

⇒ M = 1900

Also, marks of two students were wrongly copied as 34 and 23 instead of 43 and 32.

Sum of all observations = 1900

Wrongly copied numbers = 34 and 23

Subtract the wrongly copied numbers from the sum of all observations.

⇒ 1900 - (34 + 23)

⇒ 1900 - 57 = 1843

New numbers = 43 and 32

Add the new numbers to the sum of all observations

⇒ 1843 + (43 + 32)

⇒ 1843 + 75 = 1918

From above calculations, we have new sum = 1918

Now,

New mean = (New sum)/(Total number of observations)

⇒ 1918/50 = 38.36


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