In a classroom the average height of all the boys was 170 cm. Rahim recently joine the class which originally had 20 boys increased the average to 171cm. Then find the height of Rahim.

• Before Rahim joined the total height of all the boys = 170 X 20 = 3400.
  New average = (Total height of all students + height of rahim)/21 = 180
  Therefore (3400 + height of rahim)/21 = 171
  Therefore height of Rahim = 3780 - 3400 = 191 cms.
• 12 years agoHelpfull: Yes(6) No(6)
• Before Rahim joined the total height of all the boys = 170 X 20 = 3400.
  New average = (Total height of all students + height of rahim)/21 = 171
  Therefore (3400 + height of rahim)/21 = 171
  Therefore height of Rahim = 3591 - 3400 = 191 cms.
• 11 years agoHelpfull: Yes(4) No(0)
• As average of class before Rahim join is 170, now when Rahim joins average of class will be calculated for 21 boys. So let height of Rahim be x and x=171*21-170*20=3591-3400=191cm
• 8 years agoHelpfull: Yes(1) No(0)
• average height of 20 boys --170cm
  after rahim joined the new average became--171cm
  The difference in average after rahim joined is--(171-170)=1cm
  now height of rahim =(total no. of boys initially present *The difference in average after rahim joined is)+new average
  ie. height of rahim= (20*1)+171=191cm
  ans: 191cm
• 8 years agoHelpfull: Yes(0) No(0)