Question

The mean marks of 100 students were calculated as 65. At the time of checking it was found the marks 40 and 50 was wrongly copied and weeded out Find the correct mean marks.​

Answer 1

[ Because those two numbers are removed you need to reduce the number of terms to 98. ]

☆Solution☆

N=100

Mean=65

(Wrong Numbers=40,50)

Now,

Mean=Sum/No. of items

or,65=Sum/100

▪Sum=65×100=6500

After removing the unnecessary numbers,

New Sum=6500-40-50=6410

New no.of terms(N)=100-2=98

Now,

New Mean=New Sum/New N

=6410/98

=65.41

Ans.

Explanation: