the average age of A and B is 20 years.if C were to replace A,the average would be 19 and if C were to replace B,the average would be 21.what are the ages of A,B,C?

1)22,18,20  2)18,22,20

 

3)22.20,18  4)18,20,22

explain

Let x,y and z be the ages of A, B and C respectively.

 

Given that the average age of A and B is 20.

 

 

Given that the average age of B and C is 19.

 

 

Given that the average age of A and C is 21.

 

 

Substitute the value of y = 38 - z from equation (2) in equation (1), we have

 

 

Adding equations (3) and (4), we have

 

Thus, the ages of x, y and z are 22, 18, 20

 

And hence the correct option is (1).