Q. Average age of students of an adult school is 40 years. 120 new students whose average age is 32 years joined the school. As a result the average age is decreased by 4 years. Find the number of students of the school after joining of the new students:
Option
(a)1200
(b)120
(c)360
(d)240

• Let's take intial avg is 40
  intial total will be 40x
  new avg is 36
  then new total become 40x+120*32=36(x+120)
  x=120
  total students=120+120=240
  so ans is 240
  
• 11 years agoHelpfull: Yes(28) No(3)
• from the qstn
  initial avg age= 40
  new 120 stu's avg age= 32
  from the qstn new avg age = 40-4=36
  from the data we can write
  x(40)+ 120(32)=(x+120)(36)
  ==> x=120
  so total num of stu's after joining new stu's = 120+120=240
  ans is 240
  
• 11 years agoHelpfull: Yes(11) No(0)
• (n1/n2)=(A2-An)/(An-A1)
  (n1/120)=(40-36)/(36-32)
  n1=120
  There fore Total students = n1+n2=120+120=240
• 11 years agoHelpfull: Yes(9) No(2)
• formula for dis type of ques :The average age of N persons is x years.If M person joins then,the average is decreased by y years,then avg age of new comers is : x+{1+(N/M)}y years.
  Here avg age f new comers=32
  x=40
  M=120 and y=4,we can find N from the formula n den add 120 for total students.
• 11 years agoHelpfull: Yes(4) No(3)
• (40*n+32*120)/n+120=36
  n=120
  total=120+120=240
• 9 years agoHelpfull: Yes(3) No(0)
• what do u mean by adult school?Plz modify the question
• 9 years agoHelpfull: Yes(3) No(0)
• only calculation
  suppose there were x students initially
  40*x+32*120/120+x=36
  40x-36x=120*36-120*32
  4x=120(36-32)
  4x=120*4
  x=120
  total x+120
  240 ans.
  x
• 10 years agoHelpfull: Yes(2) No(2)
• 14 posts at each side. so total 56 posts . but there is 1 post common at each corner. so total 56-4 = 52 no of posts..
• 11 years agoHelpfull: Yes(0) No(3)
• 240,d option.
  120*32+40y=36(120+y); where y is no. of old students.
  solving for y.
  y=240
• 10 years agoHelpfull: Yes(0) No(0)
• ans:240
  easy way to do this is
  consider x persons for 40y
  total avg we get is 40-4=36
  32-36=-4*120=-480
  40-36*x=480
  x=120;
  120+120=140
• 10 years agoHelpfull: Yes(0) No(0)
• (d)240
  (x*40)+(120*32)=36*(120+x)
  x=120
  
  now the no of student is 120+120=240;
• 9 years agoHelpfull: Yes(0) No(0)