Question

The average age of all members of an organisation is 36years. If four new members , whose average age is 40years, joined the organisation, then the average age becomes 37years. How many members were there initially in that organisation?

Answer 1

Answer:

The number of members in the organization before the new four members are joining is $12$.

Step-by-step explanation:

Let the number of members in the organization be $x$.

So, average age of $x$ members $=36$

therefore, total age of $x$ members $=36x$

(average age=total age/number of members).

Given average age of new four members is $40$ years.

therefore total age of new four members $=4$×$40=160$

Hence total age of $x+4$ members $=36x+160$

and given average age of $x+4$ members $=37$

hence from the given information we get that

$37=(36x+160)/x+4$.  Rearranging,

 $37(x+4)=36x+160\\37x+148=36x+160\\37x-36x=160-148\\x=12$

Thank you