The average weight of boys in a class is 40 and girls is 60. The average weight of the entire class is 45. 8 new boys joined and their average weight is 80. After the addition of these new boys, the average weight increased by 7. What is the initial number of boys and girls in the class respectivel…

Question

The average weight of boys in a class is 40 and girls is 60. The average weight of the entire class is 45. 8 new boys joined and their average weight is 80. After the addition of these new boys, the average weight increased by 7. What is the initial number of boys and girls in the class respectively? Can this question be solved using Aligations?

Ajita · Answer

40     60
     45
15  :   5
3K    :   1K

80*8+120K+60K/ 4k+8 = 52
K= 8 
Boys : 24 and Girls : 8

Akarsha Mandala · Answer

Hi Meghana,
Let the initial number of boys and girls be x and y respectively.
It is given,
40x+60y/x+y = 45
5x = 15y
x = 3y
It is also given that,
40(3y) + 640 + 60y/4y + 8 = 52
Solving, we get y = 8 and x = 24
Therefore, the number of boys and girls initially is 24 and 8, respectively.
Hope this helps!

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