The average of two numbers A and B is 20, that of B and C is 19 and of C and A it is 21. What is the value of A?

• A + B
  _____ = 20
  2
  
  
  B + C
  _____ = 19
  2
  
  
  C + A
  _____ = 21
  2
  Above information is given in the problem.
  
  A + B = 40 (BY taking 2 on the opposite side)------EQUATION NO. 1
  B + C = 38 (BY taking 2 on the opposite side)------EQUATION NO. 2
  C + A = 42 (BY taking 2 on the opposite side)------EQUATION NO. 3
  
  FOR FINDIND VALUE OF ** A **
  
  A + B = 40 --------EQUATION NO. 1
  -
  C + B = 38 --------EQUATION NO. 2 (Whether you write B+C or C+B :: ALL SAME)
  ______________
  A - C = 2 [ B - (+B) = B - B = 0 ]
  
  now using this equation with EQUATION NO. 3
  
  A + C = 42 --------EQUATION NO. 3
  +
  A - C = 2 (Our very own processed equation of equation no.1 - quation no.2 )
  ______________
  2A = 44
  A = 44/2 = 22
  
  Now this is going to be very smooth...
  
  A + B = 40 ------EQUATION NO. 1 (putting the value of A ; that is 22)
  22 + B = 40 SO B = 18
  
  A + C = 42 ------EQUATION NO. 3 (putting the value of A ; that is 22)
  22 + C = 42
  C = 42 - 22 = 20
  
  A = 22
  B = 18
  C = 20
  
  Cheers 3:)
• 10 years agoHelpfull: Yes(4) No(1)
• A+B=20
  B+C=19
  C+A=21
  
  FROM 1ST EQ B=20-A,
  THRFOR PUT IT INTO 2ND EQ 20-A+C=19
  A=11 ans
  
• 10 years agoHelpfull: Yes(0) No(3)