Question

two years ago the mean age of 40 people was 11 years 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

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Here is the solution:

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Find the average age of the 40 people now:

Average age 2 years ago = 11

Average age now = 11 + 2 = 13

Find the sum of the age of the 40 people:

average = 13

sum = 13 x 40 = 520

Find the sum of the age of the 39 people:

Average = 12

Sum = 12 x 39 = 468

Find the age of the one that left the group:

Age of the person = 520 - 468 = 52

Answer: The age of that person is 52 years old

Answer 2

Mean age of 40 people was 11

let x be sum of all people of the group

x/40=11

x=440

let y be the weight of person leaving the group

x-y/39=12

as we know x=440

440-y= 468

y=28 years                      (we ignore the negation as it cannot be negative)

The person leaving the group has a weight of 28.

Hope this helps u !!!!!!!!!!!!!!!!!!!!