There are $40$ students in a class and average weight is $40 k g$ . When a boy goes away and a girl joins the class at the same time, the average weight of the class decreases by $\frac{1}{8}$ kg. Calculate the weight of the new girl.

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Solution

There are 40 students of average weight of 40 kg.
$∴$ Total weight $= (40 \times 40) k g = 1600 k g$
When a boy goes away and a girl joins the average decreases by $\frac{1}{8} k g$
Since the average was 40 kg.
then it decreases by $(40 - (40 \times \frac{1}{8})) k g = 35 k g$
Hence , the weight of the new girls is 35 kg.

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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.

There are 40 students of average weight of 40 kg.∴ Total weight =(40×40)kg=1600kgWhen a boy goes away and a girl joins the average decreases by 18kgSince the average was 40 kg.then it decreases by (40−(40×18))kg=35kgHence , the weight of the new girls is 35 kg.

There are $40$ students in a class and average weight is $40 k g$ . When a boy goes away and a girl joins the class at the same time, the average weight of the class decreases by $\frac{1}{8}$ kg. Calculate the weight of the new girl.