Question

Two years ago mean age of 40 people was 11years. now a person left the group and the mean age is changed to 12 years. Find the age of the person who left the group?​

Answer 1

Statement 1:
Two years ago the mean age of 40 people was 11 years.
So, at present the mean age will be increased by 2.
Hence the mean age at present will be 11 +2 =13 years
Statement 2 :
Now a person left the group and the mean age is changed to 12 years
We know that
Mean =