Out of seven given numbers, the average of the first four numbers is 4 and that of the last four numbers is also 4. If the average of all the seven numbers is 3, fourth number is
(1) 3
(2) 4
(3) 7
(4) 11
(5) None of these

• (a+b+c+d)/4=4
  =>(a+b+c+d)=16...........(1)
  
  (d+e+f+g)/4=4
  =>(d+e+f+g)=16
  =>(e+f+g)=16-d...........(2)
  
  Also, (a+b+c+d+e+f+g)/7=3 (Given)
  using (1) and (2) equations
  16+16-d=21
  => d=11 (answer)
• 8 years agoHelpfull: Yes(10) No(0)
• A+B+C+D/4=4;
  A+B+C+D=16; D+E+F+G=16;
  A+B+C+D+E+F+G=21;
  SOLVING D=11
  
• 8 years agoHelpfull: Yes(2) No(0)
• (x1+x2+x3+x4+x5+x6+x7)/7=3
  (x1+x2+x3+x4)/4=4
  (x1+x2+x3+x4)/4=4
  let x1+x2+x3=s1, x5+x6+x7=s2
  s1+x4=16 ------------------1
  s2+x4=16 -------------------2
  s1+x4+s2=21-----------------3
  using 1 and 2: s1+s2+2x4=32 ----------------4
  using 3: s1+s2=21-x4
  using 4: 21-x4+2x4=32
  x4=32-21=11
• 7 years agoHelpfull: Yes(1) No(0)
• Answer:
  (4) 11
• 7 years agoHelpfull: Yes(0) No(0)
• X1+X2+X3+X4 = 16 and X4+X5+X6+X7=16
  X1+X2+X3+X4+X5+X6+X7=21
  16+16-X4=21
  X4=11
• 6 years agoHelpfull: Yes(0) No(0)