In seven given numbers,the average of first four numbers is 4 and that of last four numbers is also 4. if the average of these seven numbers is 3, the fourth number is?
a.3
b.4
c.7
d.11

• let 7 numbers are a,b,c,d,e,f,g.
  given avg of first 4 nums are 4...i.e (a+b+c+d)/4=4
  a+b+c+d=16
  given avg of last 4 nums are also 4..i.e.(d+e+f+g)/4=4
  d+e+f+g=16
  e+f+g=16-d
  given avg of 7 nums are 3....i.e (a+b+c+d+e+f+g)/7=3
  a+b+c+d+e+f+g=21
  16+16-d=21
  d=32-21
  d=11 is answer
• 12 years agoHelpfull: Yes(26) No(2)
• 11
  
  
  the average of first four numbers is 4 and
  sum of first 4 numbers= 4*4=16
  that of last four numbers is also 4.
  Sum of last 4 numbers = 4*4=16
  Sum of 7 numbers + 4th number = 16+16=32
  if the average of these seven numbers is 3,
  Sum of 7 numbers = 7*3=21
  4th number = 32-21=11 .. option D
• 12 years agoHelpfull: Yes(6) No(1)
• d. 11
  x1+x2+x3+x4 = 4*4 =16
  x4+x5+x6+x7 = 4*4 =16
  x1+x2+x3+x4+x5+x6+x7 = 3*7 =21
  => x4 = 16+16-21 = 11
• 12 years agoHelpfull: Yes(3) No(2)
• let the no.s be;
  X1,X2,X3,X4,X5,X6,X7
  X1+X2+X3+X4 divided by 4=4
  there for;X1+X2+X3+X4=16 (cross multiply)
  just like that
  X4+X5+X6+X7=16
  there for;
  X1+X2+X3+X4 = X4+X5+X6+X7
  X1+X2+X3 = X5+X6+X7 (X4 is common so it is cancelled)
  X1+X2+X3+X4+X5+X6+X7 divided by 7 =3 (given in the question)
  this can be written as;
  (16 - X4) + X4 +( 16 - X4)=21 (cross multiply to get 21)
  -X4 = 21-32
  -X4 = -11
  SO,
  X4 = 11 . 4TH NO. IS 11.
• 12 years agoHelpfull: Yes(3) No(0)
• x/4=4 => x=16
  y/4=4 => y=16
  z/7=3 => z=21
  therefore the fourth no = 16+16-21= 11
• 12 years agoHelpfull: Yes(2) No(0)
• consider a b c d e f g
  avg of first 4 num (a+b+c+d)/4=4; a+b+c+d=16
  avg of last 4 num (d+e+f+g)/4=4; d+e+f+g=16
  (a+b+c+d+e+f+g)/7=3
  16+e+f+g=21;
  e+f+g=5
  a+b+c+16=21; a+b+c=5;
  5+d+5=21;
  so d is 11
• 12 years agoHelpfull: Yes(1) No(0)
• a+b+c+d+e+f+g=21
  a+b+c+d=16
  d+e+f+g=16
  a+b+c+d+e+f+g+d=21+d
  16+16=21+d
  d=11
  
  
• 11 years agoHelpfull: Yes(1) No(0)
• let forth no.=x
  average of first three nos=4-x/3
  ((4-x)/3)+4=3
  x=7
  hence forth no is 7
• 11 years agoHelpfull: Yes(0) No(2)
• 4*4+4*4-3*7=11
  
• 9 years agoHelpfull: Yes(0) No(0)
• f1=1,2,3,4 = 4 * 4 = 16;
  f2=4,5,6,7 =4*4 = 16;
  f1+f2 = 32
  
  f-total = 1,2,3,4,5,6,7 =7*3 = 21;
  .'. (f1+f2) - ftotal = 32-21 = 11;////
• 7 years agoHelpfull: Yes(0) No(0)
• 4th no=4*4+4*4-7*3
  =11
  by formula
• 6 years agoHelpfull: Yes(0) No(0)