The average weight of a group of boys is 30 kg. after a boy of weight 35 kg joins the group, the average weight of the group goes up by 1 kg. find the number of boys in the group originally ?
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Suppose there are N members in group;
Total weight= N*30
If one boy of weight 35 kg join the group;
(N+1)*31-N*30=35; (31 is new average by joining a boy)
31N+31-30N=35;
N=35-31=4 boys in group
Total weight= N*30
If one boy of weight 35 kg join the group;
(N+1)*31-N*30=35; (31 is new average by joining a boy)
31N+31-30N=35;
N=35-31=4 boys in group
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