Let the weight of the boy who left the class is x. Total weight = 50 × 45 = 2250 kg when one boy left the class total weight is (2250 – x)and no. of student left is 49. According to question –
2250−x
49
=(45−
100
1000
)kg
2250−x
49
=44.9 2250 – x = 2200.1 x = 2250 – 2200.1 x = 49.9 kg