Q. The average age of 30 boys of a class is equal to 14 yrs. When the age of the class teacher is included the average becomes 15 yrs. Find the age of the class teacher.
Option
A 40 yrs
B 42 yrs
C 45 yrs
D 46 yrs

• The average age of 30 boys of a class is equal to 14 yrs:
  i.e Sum of all boys:30*14
  
  include class teacher:31 candidates in a class
  & avg age is:15 yr
  i.e. sum of all:31*15(include class teacher)=465
  
  so,the age of the class teacher:465-420=45yr
  answer will be 45 yrs(option c)
  
• 10 years agoHelpfull: Yes(25) No(0)
• avg age of 30 boys in class is 14 yrs
  sum of ages of boys =30*14=>420
  When the age of the class teacher is included the average becomes 15 yrs
  
  sum of ages of boys=31*15=>465
  
  age of Teacher=465-420=45
  
  so answer is 45 years
• 10 years agoHelpfull: Yes(1) No(0)
• ans:45
  14=sum of ages of boys/30
  sum of ages of boys=420
  15=420+x(x is the age of teacher)/31
  x=45
  
• 10 years agoHelpfull: Yes(0) No(0)
• including-excluding
  31*15-30*14
  45
• 10 years agoHelpfull: Yes(0) No(0)
• 30*14=420
  31*16=465
  465-420=45 ans c 45
• 10 years agoHelpfull: Yes(0) No(0)
• ans: 45
  FORMULA:
  new person weight = present average+(Total number of persons+increased weight)
  = 14+(31*1)
  = 45
• 10 years agoHelpfull: Yes(0) No(0)
• From given problem total age of boys=30*14=420
  when teacher was included then total agge=(30+1)*15=465
  teacher age is=465-420=45 years
  
• 10 years agoHelpfull: Yes(0) No(0)
• let the age of class teacher =x
  30*14 + x = 15*31
  420 + x = 465
  x = 465-420 = 45years
• 8 years agoHelpfull: Yes(0) No(0)
• 45
  31×15-30-14=45
• 8 years agoHelpfull: Yes(0) No(0)
• (30*14+x)/31=15
  x=45
• 8 years agoHelpfull: Yes(0) No(1)
• 30*14=420
  31*15=465
  465-420=45years
• 7 years agoHelpfull: Yes(0) No(0)