The average of six numbers is 30.If the average of first four is 25 and that of last three is 35, the fourth number is :
A) 25 B) 30 C)35 D)40

• a+b+c+d+e+f=180
  a+b+c+d=100
  d+e+f=105
  add 2nd and 3rd equations
  a+b+c+2d+e+f=205
  solve to find d as 25
• 11 years agoHelpfull: Yes(8) No(4)
• Sum of all six no. is 180(30*6)
  sum of first four 100
  sum of last three 105
  forth no. is 100+105-180=25
• 8 years agoHelpfull: Yes(4) No(0)
• a+b+c+d+e+f=180
  a+b+c+d=100
  d+e+f=105
  from 1 and 3
  we get... a+b+c=180-105=75
  from 2 we get... d=105-75=30
• 8 years agoHelpfull: Yes(2) No(2)
• sum of six nos is 180.
  sum of first four is 100
  sum of last three is 105.
  sum of last two is 180-100=80.
  fouth one is obtained by 105-80=25.
  
• 8 years agoHelpfull: Yes(0) No(0)
• let x1,x2,x3,x4,x5,x6 are the the six no
  then
  x1+x2+x3+x4+x5+x6/6 =30
  then x1+x2+x3+x4+x5+x6=180 ----eq1
  According to the question, average of first four i.e x1,x2,x3,x4 is 25
  x1+x2+x3+x4/4 =25
  then x1+x2+x3+x4=100
  
  then by eq1 100+x5+x6=180
  x5+x6=80 -----eq2
  and x4+x5+x6=105(35*3)
  putting the value of x5+x56 from eq2
  80+x4=105
  x4=25
• 5 years agoHelpfull: Yes(0) No(0)