The average age of a class of 39 students is 15 years .If the age of the teacher be included, then the average increases by 3 months .Find the age of the teacher.
A) 25 years B) 27 years C) 35 years D) 28 years

• let assume sum of all student ages=x
  x/39=180month so x=7020;
  teacher age=y so avg.,
  (x+y)/40=183
  y=183*40-x
  y=300 month
  y=300/12=25yrs
  
• 12 years agoHelpfull: Yes(19) No(9)
• total age of 39 person = 39*15 = 585years
  age of 40 person = 15*40person+(3*40)/12(converting month into years so dividing by 12)=610years
  therofore age of the teacher = 610 - 585 = 25 years
• 11 years agoHelpfull: Yes(12) No(3)
• 39 students ------> AVG = 15
  39+1 TEACHER -------> AVG INCREASES BY (3 MONTHS/12 MONTHS)= 1/4
  1 TEACHER OUT OF 40 CAUSING CHANGE = 1/4
  1/40 = 1/4====> 1/4*40 == 10
  PREVIOUS AVERAGE = 15
  SO 15+10 = 25 YEARS
  
• 9 years agoHelpfull: Yes(5) No(0)
• (x+y)/40=183
  y=183*40-x
  y=300 month
  y=300/12=25yrs
• 10 years agoHelpfull: Yes(4) No(3)
• Assume that the sum of the ages of all the students is 'x'
  then according to the first condition,
  x/39 = 15
  by solving this we get the sum of ages of all the students is = 585.
  now by second statement,
  let 'a' be the age of the teacher.
  then, (a+585)/40 = (15 + 1/4)yrs
  where 3 months is written as 1/4 years.
  then a = 610 - 585 = 25yrs
  hence teacher is 25 yrs old,
  
• 8 years agoHelpfull: Yes(0) No(0)
• by adding teacher age the average is increased by 3 months i.e 15.3 & remaining 39 students also will increased by 0.3 months therefore
  teacher age = 15.3 + 39 * 0.3
  = 27
• 6 years agoHelpfull: Yes(0) No(1)
• First we find total age=15×39=585
  Then new person add so total person =40
  And age is increase by 3 month means 3/12
  So,
  40×15+3/12×40=610
  610-585=25 year
• 6 years agoHelpfull: Yes(0) No(0)
• After adding teacher , total members = 40
  Average age is 15.25 (As 3 months can be considered as 0.25 year)
  hence 40*0.25 = 25+15 = 25
• 6 years agoHelpfull: Yes(0) No(0)
• It is option a
• 4 years agoHelpfull: Yes(0) No(0)