The average weight of students in a class is 43 kg Four new students are admitted to the class whose...........

Quantitative Aptitude (CDS) Average

The average weight of students in a class is 43 kg. Four new students are admitted to the class whose weights are 42 kg, 36.5 kg, 39 kg and 42.5 kg respectively. Now the average weight of the students of the class is 42.5 kg. The number of students in the beginning was

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Explanation:

Let the number of students in the beginning be n
Sum of weights of n students = 43n kg
When four new students areadmitted to the class:
Sum of weights of (n + 4) students
=43n+42+36.5+39+42.5
=(43n+160)kg
∴(43n+160)/(n+4)=42.5

⇒43n+160
⇒42.5n+170
⇒0.5n=10
⇒n=20