Question

The average marks secured by 55 girls was 67. But it was discovered that an item 85 was misread as 58. What is the correct mean of marks?

Answer 1

Given total no. of observations = 55 so, we know that sum of observations/ no.of observations= mean
i.e-
$x \div 55 = 67$
x = 67× 55 =3575
given 58 is replaced by 85 so, new eq. x =3575-85+58
=3548
now new mean =
3548÷55= 64.90909
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