The average of first three numbers is thrice the fourth number. If the average of all the four numbers is 5, then find the fourth number

• (a1+a2+a3)/3= 3(a4)---------(1)
  (a1+a2+a3+a4)/4=5---------(2)
  then a1+a2+a3=9(a4)-----put in eqn 2
  a4=2---------ans
• 6 years agoHelpfull: Yes(1) No(0)
• fourth no.=2
  
• 8 years agoHelpfull: Yes(0) No(1)
• lets no. are a ,b,c,d
  (a+b+c)=3*3d=9d-------(1)
  then, (a+b+c+d)/4=5
  Instead of a+b+c we can put 9d...
  so,9d+d=4*5=20
  it means ,d=2(answer).....
• 6 years agoHelpfull: Yes(0) No(0)