Question

There are 50 boys in the class their average weight is 45kg when one boy leaves the class the averge reduces by 100g find the weight of the boy who left the class

Answer 1

the weight of the boy is 49.9kg

Answer 2

Solution :-

Total number of boys in class = 50

Average weight = 45 kg

Total weight of 50 boys = 50*45 

= 2250 kg

Now, 1 boy leaves the class, the number boys remaining = 50 - 1

= 49

Average weight reduced after leaving = 100 g or 0.1 kg

Average weight of 49 boys after 1 boy leaves = 45 - 0.1 = 44.9 kg

Total weight of 49 boys = 44.9*49 

= 2200.1 kg

Now, 

Weight of the boy who left the class = total weight of 50 boys - total weight of 49 boys 

= 2250 kg - 2200.1 kg

= 49.9 kg

So, the weight of the boy is 49.9 kg, who left the class.