The average age of A and B is 20 years. If C replace A the average would be 19 and if C replaces B the average would be 21. What are the ages of A, B and C?
A. 22, 20, 18
B. 22, 18, 20
C. 18, 20, 22
D. 18, 22, 20
E. 22, 19, 20

• A+B/2=20 A+B=40
  B+C/2=19 B+C=38
  C+A/2=21 C+A=42
  BY SUBTRACTING A+B=40 AND B+C=38 WE GET A+B-B-C=40-38 A-C=2
  BY ADDING A+C=42 AND A-C=2 WE GET 2A=44 A=22
  A+C=42 C=42-22=20 C=20
  A+B=40 B=40-22 B=18
  A=22,B=18,C=20
  
• 12 years agoHelpfull: Yes(8) No(3)
• option B
  A+B=2*20;
  C+B=2*19;
  A+C=2*21;
  By solving the above equations we get the solution
  
• 8 years agoHelpfull: Yes(0) No(1)
• A+B/2=20 A+B=40---------1
  C+B/2=19 C+B=38----------2
  C+A/2=21 C+A=42----------3
  BY SUBSTRACTING 1&2 A+B=40 AND B+C=38 WE GET A+B-B-C=40-38
  A-C=2
  NOW SOLVING A-C=2 & A+C=42
  2A=44
  A=22
  SUBSTITUTE A=22 IN A-C=2
  C=22-2
  C=20
  SUBSTITUTE C=20 IN B+C=38
  B=38-C
  B=38-20
  B=18
• 5 years agoHelpfull: Yes(0) No(0)