There
are two buildings P and Q. If 15 persons are sent from P to Q, then the number of
persons in each building is the same. If 20 persons are sent from Q to P, then the number of
persons in P is double the number of persons in Q. How many persons are there in
building P?
A. 80
B. 140
C. 120
D. 90

• p-15 = q+15
  p-q = 30 ....... (1)
  
  p+20 = 2(q-20)
  p-2q = -60 ...... (2)
  
  solving eq. (1) and (2)
  
  P = 120
  Q = 90
• 10 years agoHelpfull: Yes(21) No(1)
• Let the number of persons in building P = p
  and the number of persons in building Q = q
  If 15 persons are sent from P to Q,
  then the number of persons in each building is the same
  => p-15 = q+15
  => p - q = 30 ----(Equation 1)
  If 20 persons are sent from Q to P,
  then the number of persons in P is double the number of persons in Q
  => 2(q - 20) = (p + 20)
  => 2q - 40 = p + 20
  => 2q - p = 60 ----(Equation 2)
  (Equation 1) + (Equation 2)=> q = 90
  From Equation 1, p = 30 + q = 30 + 90 = 120
  i.e., Building P has 120 persons
  
• 10 years agoHelpfull: Yes(5) No(0)
• p-15=q+15 (1)
  p+20=2(q-20)
  q=(p+60)/2
  put the value of q in (1)
  p=120
  
• 10 years agoHelpfull: Yes(1) No(0)
• let there are x persons in building P and y persons in building Q.
  X-15=Y+15
  or,x-y=30---(1)
  2*(y-20)=x+20
  or,2y-40=x+20
  or,2y-x=60---(2)
  adding eq. (1) and (2)
  y=90
  x=120
  hence no of persons in building P are 120
• 10 years agoHelpfull: Yes(0) No(0)