The average age of 24 boys and the teacher is 15 years. When the teacher's age is excluded, the average decreases by 1. What is the age of the teacher ?

a. 38 years
b. 39 years
c. 40 years
d. Data inadequate

• Avg of boys when teacher INCLUDED = (24+1)*15 = 375
  avg of boys when teacher is EXCLUDED= 24 * 14 = 336 ( Because in Question, given that average is decreased by 1 when teacher is excluded) .
  So age of Teacher = 375-336 = 39.
  option B
• 9 years agoHelpfull: Yes(13) No(0)
• 1(teacher)+24(student)--------------15(avg)
  24(student)------------------------------14(avg)
  hence 15+24 or 25+14 ====39(ans)
• 9 years agoHelpfull: Yes(5) No(0)
• a 24*15-23*14=38
• 9 years agoHelpfull: Yes(0) No(5)
• Short cut :
  15+24*1
  =15+24
  =39
• 7 years agoHelpfull: Yes(0) No(0)
• b.39 years
• 7 years agoHelpfull: Yes(0) No(0)