There are 40 students in a class and average weight is 40kg . When a boy goes away and a girl joins the class at the same time, the average weight of the class decreases by 18kg. Calculate the weight of the new girl.
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Solution
There are 40 students of average weight of 40 kg.
∴ Total weight =(40×40)kg=1600kg
When a boy goes away and a girl joins the average decreases by 18kg