Question

2 years ago the mean age of 40 people was 11 yearsnow 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

The total age 2 years ago is 11 * 40 = 440
2 years later the present total age would be 13 * 40 = 520
but 1 person left from the group and the mean age is changed to 12
so 12 * 39 = 468
that means 520 - 468 = 52
so the age of the person who left the group is 52 years.

Answer 2

Solution :

_____________________________________________________________

Given :

Condition 1 :

2 years ago the mean age of 40 people was 11 years.

⇒ Now, the age of all 40 people will be increased by 2,.

Hence, the present mean age will be 11 + 2 = 13 years,.

___________________________________________

Condition 2 :

Now a person left the group and the mean age is changed to 12 years.

Hence, the average reduced by 1 year,.

_____________________________________________________________

To Find :

The age of the person who left the group,.

_____________________________________________________________

⇒ Let the age of the man be x years,..

As we know that,

Mean = sum of the observations/total number of obserations,.

Hence,

Initially, $\frac{total{age} (40 people)}{40} = 13$

⇒ total age of 40 = 40 x 13

⇒ Total age of 40 people = 520

______________________________

After a person left the Total age of the people = 520 - x

Mean = $\frac{520-x}{40 - 1} = 12$

⇒ $520 - x = 12 (39)$

⇒ 520 - x = 468

⇒  x = 520 - 468

⇒ x = 52,.

                        ⇒  Hence, the age of the person is 52 years,.

_____________________________________________________________

                                           Hope it Helps!!

⇒ Mark as Brainliest,.