Question

The average of two numbers is (2P-Q).If one number is P,then the other number is?

Answer 1

Let the other number be (x) 
One of the number is P 
Mean is (2P-Q)
We know that mean = sum of observations / no.of observations 
  ⇒(P+x)/2 = (2P-Q) 
  ⇒(P+x) = 2(2P-Q)
  ⇒(P+x) = 4P-2Q
  ⇒ x = 4P-2Q -P
  ⇒ x = 3P-2Q
Check :
     (P+x)/2 = (2P-Q)
     (P+3P-2Q)/2 = (2P-Q)
     (4P-2Q)/2 = (2P-Q)
     2(2P-Q)/2 = (2P-Q)
      (2P-Q) = (2P-Q)
Therefore , L.H.S = R.H.S .